Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session H71: Poster Session I (2:00pm - 4:00pm)Education On Demand Poster Undergrad Friendly
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H71.00001: UNDERGRADUATE RESEARCH
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H71.00002: Possible Role of the C60 Molecule and Fullerene Molecules in the Origin of Life Jose Pacheco, Ajit Hira, Gabriel Serrano, Alicia Fresquez, Matilda Lymon, Lucy Freeman, Ruben Rivera We continue our interest in the investigation of the molecules of biological interest, by performing computations on the properties of various complexes of C60 fullerenes with some simple organic molecules. “Minimal life’ is very difficult to define, but we consider a molecular system to be alive if it can turn resources into building blocks of life, and it can replicate and evolve. In considering how prebiotic building blocks self-assemble and transform themselves into a living system we have to address two main questions: the processes of prebiotic building blocks forming containers, metabolic networks, and informational polymers; and the organization of these three components in a protocell. We uncover here some credible cooperative mechanisms among all the aspects of protocell assembly: starting material, reaction mechanisms, thermodynamics, and the integration of the three different functionalities. We also examine the implications for origin of extraterrestrial life. We propose some laboratory experiments that might help in testing our theoretical results. Finally, we discuss possible links between the three disciplines of astro-chemistry, prebiotic chemistry, and artificial life research. |
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H71.00003: Determining Schottky Barrier Heights of 2D GaSe and GaTe with Various Metals for Improved Solar Cells Julianna Koehl, Nicole Hall, Ismaila Dabo A first-principles investigation of the electronic properties of two-dimensional gallium telluride (GaTe) and gallium selenide (GaSe) was conducted. These materials are promising candidates for photovoltaic and optoelectronic applications due to their band gaps compatible with the solar spectrum. Density-functional theory calculations were carried out to compute Schottky barrier heights at GaTe-metal and GaSe-metal interfaces and determine which one of these interfaces could maximize diode efficiency. The metals considered were aluminum, calcium, copper, palladium, and platinum. After determining the geometries of the metal-semiconductor interfaces, the Mott-Schottky approach was used to calculate the Schottky barrier heights. Determining these values in contact with different metals can facilitate device optimization for solar cells that use gallium selenide and gallium telluride as light-absorbing materials. |
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H71.00004: Binomial coefficients and Arithmetic Progression in an Alternating Series with its interpretation in Vector Space Nitika Sachdeva A series is defined using terms of arithmetic sequence taken along with binomial coefficients nCr. By deriving it in all the subsequent sections of Pascal’s hexagon, the series is extended for nCr where n,r ∈ R.Further, it is analysed in a vector space and is found to be a subspace of it. The series is studied as a scalar product of three-dimensional vectors where some of the findings are generalized for n-dimensions. |
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H71.00005: Aggregation of HEK-293 Tumorigenic Cell Line Using Sound Waves Karen Ngo, Banaz Qasab, Carlos Luna The recurrence of tumors after a surgical resection remains a problem in cancer research. Even with surgical extraction and chemotherapy, there is no guarantee of complete removal of cancer cells. Therefore, there is a need to create tools that can remove the remaining cancer cells without damaging healthy tissue. Sound has been used to trap, manipulate, move, and sort cells and nanoparticles through non-contact cell manipulation. We are interested in using sound waves as a non-contact method to aggregate cancer cells. To do so, we investigated the effects of amplitude and frequency in a custom-made acoustic chamber. |
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H71.00006: Beta-Decay of 29F: The Southern Shore of The Island of Inversion Jesse Farr The island of inversion in regards to nuclear physics refers to exotic neutron-rich nuclei that do not follow a standard configuration in the nuclear shell model. To explore this region, the 29F experiment was performed in October 2020 at NSCL in Michigan State University. This experiment studies an isotope of fluorine, 29F, in a fragmentation nuclear reaction by implanting it in a crystal detector to measure its decay. By analyzing the decay of this neutron-rich isotope, it will lead to a better understanding of its decay strength, ground state wave function, and the internal structure of 29F and other exotic nuclei near the island of inversion. The VANDLE array alongside a YSO scintillator and three clover detectors will analyze the ions for each individual event to map the decay. The clovers are fitted with thin beta-veto (Betos) plastics in order to maximize efficiency; we determined 1 mm offered the best compromise between high beta response and small gamma background. In this presentation we will show the simulations and evaluation data used to define the beta gamma response. |
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H71.00007: Decision Theory for the Mass Measurements at the Facility for Rare Isotope Beams Jesse Farr Nuclear physics facilities, like the Facility for Rare Isotopic Beams (FRIB), have access to thousands of isotopes ready to be researched. Like the name FRIB suggests, rare isotopes are of significant interest, especially ones that have not yet been experimentally observed. However, creating these rare isotopes comes with a cost, both monetary costs and time. Thus, it is advantageous to quantify the amount of information gained by studying a specific isotope in comparison with its beam time, cost, and human effort that will go into the experiment. Decision theory can achieve this goal by maximizing a utility function. We are choosing to analyze only nuclear mass measurements at FRIB, and are assuming that the most costly element is the beam time required to perform the mass measurement. In the simplest form, the information gained by a mass measurement is the change in the information content of the probability distribution of all nuclear masses. In this work, we model the information gain obtained by nuclear mass measurements from two perspectives: first from the perspective of theoretical mass models as understood by mass tabulations, and the second from the perspective of r-process nucleosynthesis. |
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H71.00008: Variation of Soil Temperature at Various Depths and Time using Mathematical model Alfred Mishi, Ezekiel K. Makama The importance of soil temperature cannot be overemphasised, as it is fundamental in determining seeds and crops germination and growth. In this work, temperature at four different soil depths are empirically predicted using the one-dimensional heat flux equation, with mean monthly temperature from the University of Jos Weather Station. The model performed best at the 5 cm depth with a mean bias error (MBE) of -0.67 cm and root mean squared error (RMSE) of 1.18 cm, and coefficient of determination (R2) of 0.83. The worse performance is obtained at the 10 cm depth with respective MBE and RMSE of -0.85 and 1.55 cm and R2 of 0.76. Whereas, soil temperature at all the depths are found to peak in March/April with a dip in September/October at the monthly cycle, highest value (31.8 0C) which occurred at the 5 cm depth was found in 1993 with the least (19.0 0C) at the 50 cm depth in 1991. |
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H71.00009: Studying thermal effects of laser excitation power on carbonaceous meteorites by Raman spectroscopy Mohamed Zakariya, Conan Bock, Rohil Kayastha, Analía Dall'Asén Carbonaceous chondritic meteorites can provide valuable clues about planet formation since they are considered some of the most primitive surviving materials of our solar system. This information can be obtained through their physical properties which can be characterized using microscopy and spectroscopy techniques. In particular, Raman spectroscopy has been used extensively on meteoritic samples since it is a nondestructive tool that provides information about their structure and mineralogical composition. However, the power of the laser excitation source used in this technique can alter the properties of the samples due to thermal effects. Hence, it is critical to analyze in detail what alterations could be produced in a meteoritic sample due to the laser power to obtain reliable information about its physical properties, and thus, provide the right evidence to understand the origin of these relics. In this work, we study in detail the laser-induced thermal effects produced on carbonaceous chondritic meteorites by analyzing the Raman spectra parameters of the minerals found in these samples as a function of the laser excitation power and correlating them with changes that can occur on the topography of the irradiated regions using optical microscopy. |
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H71.00010: Quantum Inspired Wavelet Transformations for Image Compression James McCord, Glen Evenbly Methods involving coarse-graining transformations and the real-space renormalization group (RG) have proved essential in our understanding of phase transitions and the physics of systems at different length scales. The multi-scale entanglement renormalization ansatz (MERA), a modern realization of the RG formulated in terms of quantum circuits, has been developed to efficiently describe scale-invariant critical systems and lattice conformal field theories. Recently, a precise connection has been established between MERA quantum circuits and various multiresolution analysis (MRA) techniques used in signal and image processing, such as discrete wavelet transforms (DWTs). |
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H71.00011: Determination of the Lowest Energy Orientation of Pentacene on Graphene Jacob Martin, Bradley Lockhart, Jessica Bickel Organic semiconductors are advantageous over their inorganic counterparts due to their eco-friendliness, cheap producibility, and applications in flexible electronics. However, organic semiconductors tend to have a lower conductivity than their inorganic counterparts. One method to increase the conductivity of organic semiconductors is self-assembly driven by a surface reconstruction. As an atomically smooth surface is needed to organize organic molecules, a possible starting point is to examine the deposition of an organic molecule on graphene or graphite. This work utilizes computational calculations run in parallel to experimental growths to examine how pentacene self-organizes on graphite. The computational experiments were done with the Vienna Ab initio Simulation Package (VASP) where molecules were both translated and rotated to find the lowest energy orientation of pentacene on a graphene sheet. These results are compared to experimental results of pentacene deposited on highly ordered pyrolytic graphite (HOPG) and examined via scanning tunneling microscopy (STM). |
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H71.00012: Scanning Majorana Microscope Experiments and Data Analysis Kaedon Cleland-Host, Eric Goodwin, Michael Gottschalk, Stuart Holden Tessmer Majorana zero modes are being studied as a potential qubit for a next-generation topological quantum computer. Protected by topology and particle-hole symmetry, Majorana zero modes are insensitive to local perturbations, unlike typical qubit architectures. The Scanning Majorana Microscope is a novel technique developed to detect a unique signature of Majorana zero modes. The microscope uses a sensitive charge-sensing circuit to count individual electrons entering a metallic quantum dot on the tip of a glass scanning probe. Due to a small signal size on the scale of attofarads, up to two thousand curves are required. Previously, data intake and analysis required a lot of manual work to average these curves together. This project uses Python to quantitatively analyze this data quickly. This analysis produces a capacitance signal with a series of distinct peaks and a flat baseline. Once a capacitance peak is isolated from the averages, indicating a single electron tunneling into the quantum dot, a Python script is used to fit the peak against an experimental model for single-electron peaks, which incorporates thermal broadening and an RC integration effect. |
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H71.00013: Two-scale factor universality in O2: experiments under density gradient Seth Zoppelt, Ana Oprisan, Gurunath Gandikota, Denis Chatain, Daniel Beysens, Yves Garrabos In this study, we show that light transmission measurements directly on the image |
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H71.00014: REU: Synthesis, Assembly and Characterization of Soft Matter Systems Jessica Bickel, Kiril Streletzky Researchers at Cleveland State University’s Dept. of Physics and Dept. of Chemical & Biomedical Engineering collaboratively study unique properties and applications of soft matter materials through an NSF-sponsored Research Experiences for Undergraduates (REU) site “Synthesis, Assembly and Characterization of Soft Matter Systems”. Our REU involves physics and engineering majors in meaningful interdisciplinary research in soft matter science and engineering. The primary goal is to encourage students to continue to STEM graduate programs or workforce. REU participants benefit from CSU’s strong culture of support for undergraduate research. Students receive one-on-one mentoring from experienced faculty and participate in a variety of professional development opportunities. This poster highlights student research accomplishments and outcomes. The 26 students from three REU cohorts have, to date, contributed to 80 presentations, 6 peer-reviewed publications, 5 manuscripts submitted/in preparation, 2 peer-reviewed abstracts, and a utility patent application. Further, as of Fall 2020, 50% of the REU alumni are in graduate school, 15% are employed in STEM, and another 27% plan to go to graduate school after completing their bachelor's degree. |
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H71.00015: Study of Inverse Laplace Transform Analysis of NMR Magnetization Data Hyeonseon Choi, Cameron Chaffey, Igor Vinograd, Nicholas Curro We investigate the effectiveness of the Inverse Laplace Transform (ILT) analysis of NMR magnetization data in obtaining spin-lattice relaxation rate (W1) distributions. The ILT analysis method provides an estimation of the probability distribution of W1, which is significant in the study of condensed matter systems such as high-temperature superconductors. To observe the effectiveness of the method, we compare the probability distributions obtained for spin magnetization recovery curves of spin ½ nuclei with a stretched exponential form to analytic solutions of the distributions. For further study of the method, parameters such as the number of points and noise for the recovery curves are varied to observe their effect on the estimation of the probability distribution. We observe that these parameters contribute to unwanted oscillatory behavior in the estimated probability distribution solved using the ILT analysis method. |
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H71.00016: Investigation of Plasmonic Resonances in Metal Nanoparticle Embedded CdS/CdTe Solar Cells Jasmyne Emerson, Faith O Akinlade, Matthew Herrington, Venise Jan Castillon, Mehmet Alper Sahiner The addition of embedded metal (Au, Ag) nanoparticles in CdS/CdTe thin film solar cells has been shown to exhibit enhancement in the solar cell efficiency in our previous studies using pulsed laser deposition techniques. In this study we theoretically investigate the effects of these metal and semiconductor nanoparticles (Si, SiGe) on enhancement of plasmonic resonances for these photovoltaic materials. This is done through the use of computational simulation programs by designing thin films of the same structure with embedded metal and semiconductor nanoparticles. The purpose of this study is to vary size and coverage of the CdS/CdTe interface and computationally calculate the effect of these variations on the plasmonic resonances and thus solar cell efficiencies. These computational results process will be used as a pre-cursor to the experimental process of embedded nanoparticles into CdS/ CdTe through the method of Pulsed Laser Deposition (PLD). |
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H71.00017: Design and Construction of Electronics for Measuring Superconducting-to-Normal State Switching Statistics of a Josephson junction Erik Cauley, Keeran Ramanathan, Dan Fauni, Roberto Ramos
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H71.00018: Moiré Patterns in Domain Structures of Twisted Ferroelectric Bilayers Zane Bayer, Tiannan Yang, Bo Wang, Long-Qing Chen Twisting two layers of graphene by a magic angle has given rise to emergent microstructures and material properties such as unconventional superconductivity. Here, we predict the emergence of moiré patterns in the domain structure of twisted ferroelectric BaTiO3 bilayers of nanometer thickness using phase-field simulations incorporating the Landau theory of ferroelectrics. We find that regular domain structures with excellent two-dimensional periodicity can spontaneously form when the two layers both containing original one-dimensional stripe domains are twisted by 30° , showing a mesoscale moiré pattern of ferroelectric domain walls. This superstructure has eight degenerate variants that can be achieved by tuning the initial poling field and these variants may coexist to assemble into more complicated polar textures. Additionally, transition between degenerate states by applying external fields is demonstrated. This computational discovery of novel domain structures opens up new avenues for nanoelectronics and twistronics based on twisted ferroelectric bilayers. |
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H71.00019: Computational prediction of a new topological ternary compound from first-principles Jack Howard, Cornelia Jerresand, Joshua Steier, Kalani Hettiarachchilage, Neel Haldolaarachchige Dirac materials have recently become a hot topic in quantum matter nature. Predicting new topological materials is critically needed for this rapidly developing field of studies. We predict a new ternary compound that shows topological properties by using computational ab initio methods. The compound is modeled by keeping the well-known ZrSiS tetragonal structure of non-symmorphic space group p4/nmm. In the first Brillouin-zone, multiple Dirac-like crossings near the Fermi energy were identified by considering the effect of spin-orbit coupling toward the linear crossing. Additionally, we perform formation energy calculation and elastic property calculations to confirm that the compound is experimentally realizable. The compound will be useful to study for novel Dirac Fermions in the future. |
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H71.00020: Studying Diffusion of Particles in Solution by SEM and DLS Samantha Tietjen, Richard Sent, Petru Stefan Fodor, Kiril Streletzky Microgels are polymer-based nanoparticles that exhibit a reversible volume phase transition in water. Dynamic light scattering (DLS) measures collective particle diffusion in a sample yielding microgel structure and dynamics. DLS is optimized for monodisperse and dilute samples. Scanning electron microscopy (SEM) can provide images of individual microgels but uses high vacuum conditions. There are two main drawbacks of microgel dry imaging: dehydrated particles deswell and their dynamics are not observable. To counter this, wet particle imaging in an ionic liquid was explored. Still images and movies of particles suspended in a thin film of ionic liquid on a copper grid were recorded to analyze particle size distribution and dynamics. Average microgel size from DLS and SEM agreed in ionic liquid and water at room temperature. Particle diffusion was studied by tracking its mean square displacement in ionic liquid. Silica spheres were used as a control due to their stable nature. For a large sample volume, average diffusion coefficient of tracked silica particles agreed with DLS results, but varied for individual particles. Microgels proved to be a more complicated system, exhibiting complex behavior such as clustering, drift, rotation, and motion quenching. |
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H71.00021: Simulation of Programmable Matter with Mathematical Graphs Cesar Meza, Jorge Munoz The prospect of programming matter provides an unprecedented array of potential uses in architecture, mechanical engineering, and other scientific disciplines dedicated to the creation of future technologies. Therefore, multiple firms and institutions have spearheaded efforts to develop dynamic materials and compounds easily mutable in structure with a simple, selected stimulus. This work attempts to predict the possibility of actuating programmable materials on an atomic scale, simulating the mechanics of a sixty-four-node, cubic lattice structure. Coded using the Python-based NetworkX library, each node and edge represent the particles of a selected element and the forces between each atom, respectively; the program encodes mass attributes to each node and a spring constant to each edge, values of which – by use of Hooke’s law – determine the behavior of the system upon the introduction of a simulated phonon or elastic collision. Eventually, through experimentation with discrete masses, forces, and elastic vibrations, this program demonstrates possible input combinations that change the lattice structure to a predetermined shape, leading to the possibility of replicating the simulated relationships and, hence, providing an innovative manner of manipulating matter, atom by atom. |
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H71.00022: Ionic liquid gel gate tunable p-Si/MoS2 heterojunction p-n diode Kelotchi Sebastian Figueroa Nieves, Nicholas Pinto, Chengyu Wen, charlie T johnson, Meng Qiang Zhao Monolayer MoS2 crystals investigated in this work were grown via chemical vapor deposition on Si/SiO2 substrates. Using a wet KOH etch, these crystals were transferred on to the edge of a freshly cleaved p-Si/SiO2 wafer where they formed mechanically robust heterojunctions at the p-Si/MoS2 interface. Electrical characterization of the device across the junction yielded an asymmetric I-V response similar to a p-n diode. The I-V response was electrostatically tunable via an ionic liquid gel gate. This is the first report demonstrating reversible gate control of the p-Si/MoS2 diode current by several orders of magnitude while lowering its turn-on voltage. Fermi energy level shifts within the MoS2 band gap by the gate was believed responsible for the observed effects. The ease of fabrication, low operating voltages (< ±2V) and moderately high throughput currents (~ 1mA) are attractive features of this diode, especially for use in sensors and power saving electronics. |
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H71.00023: Controlled doping of graphene by impurity charge compensation via a polarized ferroelectric polymer Kelotchi Sebastian Figueroa Nieves, Nicholas Pinto, Srinivas Mandyam, Meng Qiang Zhao, Chengyu Wen, Paul Masih Das, Zhaoli Gao, Marija Drndic, charlie T johnson A simple technique of doping graphene by manipulating the adsorbed impurity charges is presented. Using a field effect transistor configuration, controlled polarization of a ferroelectric polymer gate is used to compensate and neutralize charges of one type. The uncompensated charges of the opposite type then dope graphene. Both n- and p- type doping are possible by this method which is non-destructive and reversible. We observe a change in n-type dopant concentration of 8x1012 cm-2 and a change in electron mobility of 650%. The electron and hole mobility are inversely proportional to the impurity concentration as predicted by theory. Selective doping of graphene can be achieved using this method by patterning gate electrodes at strategic locations and programming them independently. Such charge control without introducing hard junctions therefore permits seamless integration of multiple devices on a continuous graphene film. |
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H71.00024: Refractive Index of Photo-thermo-refractive Glass Zayne Parsons, David E. Zelmon, Said Elhamri, Vadim Smirnov, Dan Perlov Photo-thermo-refractive (PTR) glass is used to fabricate volume Bragg gratings. The gratings are formed by exposing PTR glass to UV light interference patterns and then annealing the glass. This produces a grating by locally modulating the refractive index. The diffraction efficiency of these gratings is dependent on the refractive index modulation amplitude. We report the refractive indices of unprocessed and processed PTR glass at wavelengths from 0.4 to 4.6 microns and discuss their uses in specifying VBGs for laser beam combining |
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H71.00025: Spectral dependence of the Verdet coefficients of Terbium Gallium Garnet and Potassium Terbium Fluoride Michael Mueller, David E. Zelmon, Said Elhamri, Kevin Stevens, Gregory Foundos High power laser systems require the use of optical isolators to prevent coupling of reflected light into the pump laser. Terbium Gallium Garnet (TGG) and Potassium Terbium Fluoride (KTF) are materials used as optical isolators and while they have been grown for many years, advances in crystal growth and processing make a new set of measurements of the Verdet coefficients of these materials desirable. We present new measurements of the Verdet coefficients of TGG and KTF from 0.405 μ to 1.55 μ and derive expressions for the spectral behavior of the Verdet coefficients. |
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H71.00026: Application of Edge Detection Techniques to ARPES Data Analysis Luis Persaud, Christopher Sims, Firoza Kabir, Gyanendra Dhakal, Klauss Dimitri, Sabin Regmi, Md Mofazzel Hosen, Yangyang Liu, Madhab Neupane Well known edge detection and similar image analysis techniques can be applied to Angle Resolved Photoemission Spectroscopy (ARPES) data to achieve a result similar to that achieved through other, more computationally intensive methods and with more generality. Without applying any form of image analysis, the interpretation of ARPES data is left to the eyes of researchers and can be tricky and unreliable due to many sources of noise and distortion from the experimental processes, as a result, some of the finer, defining details required to classify a material can be missed. By applying these edge detection techniques, we are able to highlight key features such as distinct clustered bands and other fine details which may have otherwise been obscured. Here we show the implementations of various well known image processesing techniques applied to ARPES data and how they not only aid the interpretation of results, but can be looked upon as the stepping stones to more efficient data processing techniques and potential automation of the classification of quantum materials through analysis of ARPES data. |
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H71.00027: Frequency Response of a Magnetostrictive Ferromagnet-Polymer Composite Sauviz Alaei, Thomas Richardson, E. Dan Dahlberg A magnetostrictive ferromagnet-polymer composite was previously found to exhibit large, reversible magnetostrictive strain, with a maximum strain of about 60%, upon application of DC magnetic fields on the order of 5kOe.1 The composite consisted of steel wires suspended in a polymer matrix with random orientation. Reported here are the results of a study of the frequency response of the magnetostriction of samples from the above mentioned research. The amplitude of the magnetostrictive oscillation was measured as a function of the applied AC magnetic field frequency from 1.5Hz to 35Hz, with a constant AC magnetic field magnitude of 85Oe rms. This magnetic field had a magnitude less than that necessary to reach the linear response regime found in the DC magnetostriction study.1 For each sample that was measured, a resonant peak was observed at approximately 20Hz. The low frequency response differed from that expected of a damped simple harmonic oscillator. |
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H71.00028: Chirality-dependent electron redistribution in defective graphene Claire Andreasen, Md Hossain Researchers have investigated the mechanical and electronic properties of pristine graphene under stress, however, there is little research on the chirality effects on electron distribution in defective graphene under applied stress. Using density functional theory simulations and the Mulliken charge analysis, we study the electronic behavior of an isolated defect in graphene under the uniaxial loading condition for five different chiralities of the lattice. We analyze how chirality and intensity of loading affect the mechanical properties, bond length and bond angle change, and charge distributions surrounding the vacancy. Our results show that there is a uniform pattern for bond length redistribution as well as electron redistribution at all orientation angles and that such bond and electron redistributions are directly correlated. During all simulations, we observe a bond reattachment at higher deformation. In terms of the orientation angle, we demonstrate that increased orientation angle yields changes in the strength, toughness, stiffness, bond distributions, and electronics surrounding a mono vacancy. We also find that differing orientation angles result in different failure processes and speeds. |
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H71.00029: Cluster Modeling of Nickel-Gold-Copper Plasmas Arrick Gonzales, Ajit Hira, Danny Fernandez, Jose Pachco, Lucy Freeman, Mario Valerio, Ramakrishna Khalsa We extend our research on the properties of metallic materials in this paper on the physics and chemistry of small NilAumCun clusters (1=< l =<.8; 1=< m =<8; 1=< n =<.8). Nickel-gold mixtures and alloys are of considerable interest for applications such as catalysts for CO Oxidation and Water-Gas Shift Reactions, catalysts for self-assembled growth of highly ordered silicon nanotubes (SiNT), and the manufacture of metal-insulator-metal (MIM) diodes. We used a combination of theoretical techniques, including ab-initio Density Functional Theory (DFT) and Pseudo Potential Methods (PPM), to the calculate the relevant physical and chemical properties of these clusters. Properties reported here include binding energies, optimal geometries, and bond-lengths for the clusters. We examined both neutral and ionic clusters. We propose some laboratory experiments that might help in testing our theoretical results. Finally, we consider the possible implication of this work for the internal composition of neutron stars and other exotic astronomical objects. |
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H71.00030: Cellular Automata, Quantum Circuits, and Chaos. Justin Peterkin, Sarang Gopalakrishnan The goal of this experiment is to study the statistical nature and dynamics of classical and quantum cellular automata (CA). CA are discrete models, composed of cells that govern their replication and destruction. These models are useful for simulating natural sequences. Cells in these systems change states depending on the configurations of their neighbors. Location interactions between neighbors translate to global changes. Classically, cells can occupy a fixed number of states. In the quantum case, cells act like qubits and can occupy infinitely many states. This project will use code in Python, Julia, and C++ to generate multiple iterations of these evolving systems. This project will test to see which interactions and conditions tend to drive systems to chaos and others to stability. |
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H71.00031: Ionic liquid gating of electro-spun camphor sulphonic acid doped polyaniline/polyethylene oxide nanofiber field effect transistor Alejandro Cruz-Arzon, Nicholas Pinto Electrospinning was used to fabricate nanofibers of camphor sulphonic acid doped polyaniline/polyethylene oxide (PANi-CSA/PEO) composites. The PEO concentration in the composite nanofiber was 22wt%. Individual fibers were captured on gold pre-patterned Si+/SiO2 substrate and electrically characterized in a field effect transistor (FET) configuration using a back gate. The same fibers were also electrically characterized using an ionic liquid (IL) top gate. An ionic liquid was chosen because it has a high specific capacitance that reduces the operating voltages considerably. The device operational voltages were in the range ±2V. The electrical characterization of PANi-CSA/PEO nanofibers with IL gating has not been reported before, and in this poster we shall compare the device parameters (on/off ratio, mobility, threshold voltage and the sub-threshold swing) of drop cast thin film, spun cast thin film and electro-spun nanofiber FET. |
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H71.00032: Simulation of Nonlinear Lithography Process Mateo Murillo, Sean James Bentley A detailed numerical simulation of a proposed high-resolution nonlinear lithographic system was performed. The process can create arbitrary 2-D patterns at a resolution better than the traditional Rayleigh limit as was shown in the simulation. The simulation is based on realistic material properties and accounts for diffraction and other experimental limitations. Results of the simulation will be presented, along with discussion of how experimental verification of the process can be performed in a subsequent phase of the research. |
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H71.00033: Obtaining correlation between orientation of sperm and the direction of the movement using machine learning Markus Wilson, Vijay Singh, Chih Kuan Tung In polar active matter, the orientation of the front-aft asymmetric body and the direction of the velocity that the body is moving toward are typically assumed to be the same. Here, we use swimming sperm as an experimental model to examine how good this assumption is. We utilize SLEAP (Social LEAP Estimates Animal Pose), a deep learning image processing tool, to obtain sperm location and orientation from experimental video data. At each frame, the machine learning algorithm tracks the head (acrosome), the body (the flagellum meets the head or centriole), the mid-piece of the flagellum meets the principal piece, and one point on the principal piece of the flagellum. The position of the cell is defined as the head position and the orientation is given by the vector direction from the body to the head. Direction of the sperm moving velocity is calculated using the position time series between consecutive frames. We found the deviation between the two measures to be (7± 6)°. We conclude that the two directions are highly correlated and only differ from each other minimally, while the origin and influence of the small difference need to be explored in further study. |
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H71.00034: Physical pressure and chemical doping effects on electronic and magnetic properties of rare-earth-based Heusler compound (Au2PrIn) by using computational methods Jaeyoung Hwang, Neel Haldolaarachchige, Kalani Hettiarachchilage
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H71.00035: EARLY CAREER
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H71.00036: Experience Sharing: Machine Learning for Recommendation System Yue Zhang Recommendation System is one of the most important applications of machine learning in industry. A successful recommendation needs expertises from different aspects: product analysis, data reliability, algorithm and etc. Powered with these skills, machine learning engineers build comprehensive recommendation system. |
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H71.00037: Visualizing a Cooper-Pair Density Wave State in NbSe2 Xiaolong Liu, Yi Xue Chong, Rahul Sharma, J.C. Séamus Davis Transition-metal dichalcogenides (TMDs) have emerged as a rich platform hosting novel states of quantum matter. One such is the Cooper-pair density wave (PDW) state in which the electron-pair density spatially modulates at one or more wavevectors. Using atomic-resolution scanned Josephson- tunneling microscopy, we visualize the electron-pair density and discover a PDW state in the canonical TMD superconductor NbSe2. We show that the PDW shares the wavevectors of the preexisting charge density wave (CDW) and is directly coupled to the background superconductivity as evidenced by their mutual decay into a superconducting vortex core. However, simultaneous PDW and CDW imaging reveals them to be spatially distinct at atomic-scale due to a global spatial phase difference |δΦΙ≈2π/3 (one unit cell) between the two states. Given the abundance of TMDs sustaining both CDW and superconductivity, detection and visualization of PDW in NbSe2 presages abundant new PDW physics. |
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H71.00038: Interfaces beyond the elastic approximation Nirvana Caballero The framework of disordered elastic systems is widely used to describe the physics of very diverse systems with typical scales ranging from nanometers to kilometers. However, this approach has the limitation that is only applicable to univalued and smooth interfaces, thus inducing uncontrolled approximations. Solving interface dynamics and statics in more realistic systems beyond the elastic approximation is still a largely open theoretical/analytical problem. We propose to address this problem by analyzing a Ginzburg-Landau model that allows us to extend the theory of disordered elastic systems. We show the connection of our approach with the disordered elastic systems theory [1]. In addition, we show how through this connection it is possible to explain otherwise not-understood experimental results in ferromagnetic interfaces [2]. Our approach also allows us to unravel properties of migrating epithelial rat cells-fronts, by treating its boundaries as interfaces moving in a disordered landscape [3]. |
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H71.00039: Amplitude Nanofriction Spectroscopy Antoine Lainé Friction at the macroscopic scale originates from the mechanical and tribological response of single micro- to nano-scale single contacts. Consequently atomic scale friction rises as an indispensable component for large scale friction understanding as well as for the ever-growing nanotechnology fields. The interfacial sliding dynamics bears several successive live phases: from static pinning, to depinning and transient evolution, eventually ushering in steady state kinetic friction. While standard tip-based atomic force microscopy generally addresses the steady state, the prior intermediate steps are much less explored. We present here an experimental and simulation approach, taking advantage of a high frequency oscillatory imposed strain to obtain a one-shot investigation of all these successive interfacial responses. Few atoms gold contacts sliding on graphite are used to uncover the phenomena that bridge the gap between initial depinning and large speed sliding. Our findings unveil dynamical response reminiscent of thermolubric behavior at very small contact size and superlubric response for contacts larger than the graphic unit cell. The results pave the way to important insights in the understanding of atomic scale time and magnitude dependent rheology. |
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H71.00040: Combining multireference methods with the density matrix renormalization group Henrik Larsson, Huanchen Zhai, Garnet Chan Standard multireference methods are limited by the size of the active orbital space. |
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H71.00041: Field-induced freezing in the unfrustrated Ising antiferromagnet Adam Iaizzi We study instantaneous quenches from infinite temperature to well below Tc in the two-dimensional (2D) square lattice Ising antiferromagnet in the presence of a longitudinal external magnetic field. Under single-spin-flip Metropolis algorithm Monte Carlo dynamics, this protocol produces a pair of metastable magnetization plateaus that prevent the system from reaching the equilibrium ground state except for some special values of the field. This occurs despite the absence of intrinsic disorder or frustration. We explain the plateaus in terms of local spin configurations that are stable under the dynamics. Although the details of the plateaus depend on the update scheme, the underlying principle governing the breakdown of ergodicity is quite general and provides a broader paradigm for understanding failures of ergodicity in Monte Carlo dynamics. See also: Iaizzi, Phys. Rev. E 102 032112 (2020), doi: 10.1103/PhysRevE.102.032112 |
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H71.00042: Physics-based models and simulations of cancer drug response in solid tumors Aminur Rahman, erdi kara, Eugenio Aulisa, Souparno Ghosh Over the past few decades, cancer related deaths have fallen significantly as noted by the National Cancer Institute. However, assessing cancer treatments is still predominantly a trial and error process. This approach may result in delays to administer the correct treatment, the use of more invasive procedures than necessary, or an increase in toxicity due to superfluous treatments. Although these procedures may end up saving the patient, the treatment may also have an adverse effect on their quality of life. Relaible mechanistic models of drug response can potentially be used to aid oncologists and doctors in deciding on an optimal treatment strategy for the patient. We develop a modeling framework for tumor ablation, and present coupled transport - population models of varying complexity. First, we present a radially symmetric drug diffusion and binary cell death model, which produces a theoretical dose for optimal effiacy to toxicity ratios. Further, we investigate inhomogeneous - anisotropic drug diffusion, and develop an algorithm to locate the optimal injection points. Finally, we derive stochastic tumor population models that can be coupled to transport models in our framework. Importantly, the mechanistic models outperform data-driven models in statistical tests. |
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H71.00043: Calculating Transport Coefficients from Biased Molecular Dynamics Ernesto Carlos Cortes Morales, Jonathan Whitmer Molecular simulation is a fantastic tool for understanding the link between atomic details and macroscopic properties. Determination of transport properties remains a challenge, due to the long time scales needed to obtain convergent results in commonly used methods, such as equilibrium molecular dynamics simulations combined with the Green-Kubo (GK) formalism. The long timescales over which autocorrelation functions must be measured for GK is especially exacerbated when dynamics are slow due to molecular complexity or proximity to a glass transition. Here, we explore the long-time behavior of transport properties by averaging over an ensemble of short-time trajectories calculated using the GK equation, each re-weighting the ensemble-average by calculating the effective free energy of the local configuration. We explore useful parameters for determining the cutoff time for the short simulations, and methods by which the weight can be efficiently computed. The technique is then applied to calculate shear viscosity for a set of idealized systems, including a Kob-Andersen mixture prepared near the glassy state. |
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H71.00044: Tuning the surface energetics of the BiVO4 (010) surface: A joint computational and experimental study Wennie Wang, Dongho Lee, Chenyu Zhou, Xiao Tong, Emily Chen, Marco Favaro, David Starr, Kyoung-Shin Choi, Mingzhao Liu, Giulia Galli
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H71.00045: Computational Reverse-Engineering Analysis for Scattering Experiments (CREASE) Applied to Self-Assembled Polymer-peptide Conjugate Solutions Ziyu Ye, Arthi Jayaraman Engineering amphiphilic polymers in solution gives rise to a wide range of applications such as drug delivery and hydrogels. The precise characterization of the self-assembled nanostructures (e.g. via small angle scattering techniques and microscopy) is key to the design of these materials with controllable morphologies. We apply recent extensions of Computational Reverse-Engineering Analysis for Scattering Experiments (CREASE) to quantify the bilayer and vesicle structures within self-assembled polymer-peptide conjugate solutions. CREASE takes in scattering intensity profiles and polymer chemistries as inputs for a genetic algorithm to determine the peptide amphiphile bilayer composition and vesicle dimensions (e.g. core diameter, layer thicknesses) and then feeds the outcome to molecular reconstruction simulations to access molecular level conformations within the nanostructure (e.g. radii of gyration, chain packing, monomer concentration profiles). This method ties scattering profile features directly to molecular details in complex nanostructures without the need for off-the-shelf scattering models and provides chain and monomer structural information that is difficult to obtain through scattering and microscopy alone. |
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H71.00046: Energy Dissipation Through Charge Density Waves on 1T-TaS2 Dilek Yildiz, Marcin Kisiel, Urs Gysin, Ernst Meyer Non-contact energy dissipation can be measured by a highly sensitive cantilever oscillating like a tiny pendulum over the surface [1]. Dissipative nature of layered systems, such as charge density wave (CDW) systems await to be investigated. Different phases of CDW on 1T-TaS2, a layered transition metal dichalcogenide (TMD), can be observed at different temperatures. We studied the origin of non-contact energy dissipation mechanisms on nearly-commensurate and commensurate CDW on 1T-TaS2. While Joule dissipation is dominant mechanism on commensurate CDW phase, fluctuation driven dissipation is the main mechanism on nearly-commensurate CDW phase. The spectroscopy performed on nearly commensurate phase of CDW indicates that the source of the fluctuating force and dissipation is the collective movement of weakly pinned charge density waves at room temperature. |
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H71.00047: PHYSICS EDUCATION
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H71.00048: Computational Practices in Science Disciplines Claudia Fracchiolla, Claire Mullen, Maria Meehan
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H71.00049: Learning physics by experiment: VII. Moment of inertia (Student edition) Saami Shaibani This paper is a companion to one having a similar title with “Instructor edition”. The reason for having two separate papers is that their combination would otherwise interrupt the flow of each part at the expense of the other. Details are provided here of various experiments, which examine the effect of mass, length, radius, shape and density when one or more of the other parameters is kept constant. Challenges identified in the companion paper were tackled directly by the endeavor and tenacity of students, who engaged in robust discussions to maximize understanding even when results were ambiguous and/or inconclusive. As with many experimental undertakings, there was considerable trial and error; however, student progress and learning were evident in abundance, thereby increasing the success of the philosophy reported in earlier work[1-8]. |
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H71.00050: Common mistakes of adding up vectors of acceleration Ibrahim Hanna A mathematical example of incorrect management of acceleration vectors is the Special Relativity Assumption that if a train rider drops a stone off his carriage while moving in a uniform motion, he will see it moving in a straight line. However, the better expectation, mathematically, is that he will see it moving in a parabola, just like any other outside observer. When either an observer or a projectile, subjected to at least one different acceleration, the observed path of projectile follows a mathematical equation of the second degree, which represent a parabolic curve line on an ( X-Y ) coordinates. |
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H71.00051: Pivoting an REU to a Summer Research Preparation and Professional Development Program during a Pandemic Kirstin Purdy Drew, Tiffany Mathews, Kristin Dreyer In the Summer of 2020, as a result of the Covid-19 pandemic, we made a rapid pivot for our Physics and Materials NSF funded Research Experience for Undergraduates (REU) from an in-person 10-week research experience to a 2-part fully online program. In one-part, senior undergraduate students participated in an online computational research project with supplementary research oriented professional development activities. In the second online program, students, who were not engaged with online research, participated in a three-part research preparation and professional development program that focused on STEM career preparation, outreach and engagement, and scientific communication skills. The online research prep and professional development program was tailored for undergraduate and master’s students from diverse backgrounds, institutions, and disciplines. Here we present details of the structure and content of the program, and some preliminary evaluation and feedback from participants. |
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H71.00052: Students’ perspectives on online physics labs: a case study from a community college Mahendra Thapa During the face to face teaching before the pandemic started, many physics instructors might have regularly used videos and online labs in the active learning approaches of teaching of lectures and labs. These were powerful tools to visualize abstract concepts in the classroom and sometimes to substitute hands on labs when physical equipment was malfunctioning or unavailable. During pandemic, most of us were heavily dependent on online/remote labs from sources such as PhET Interactive Simulation sand Pivot interactives as an alternative of hands on labs. Although the online/remote labs may not replace the hands-on lab in terms of gaining practical experiences, a study has been conducted in a community college to better understand how these labs were helpful in mastering the course content. The assessments such lab reports of the students were analyzed and a survey was also conducted for the students’ reflection on these labs. Because of small population of the students and limited time of study, the results may not be generalized but the initial analysis showed that most of the students have positive attitude towards the online labs and they are fundamental in understanding the physics concepts. The complete analysis will couple the analysis from a four-year institution. |
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H71.00053: Reforming Introductory Physics for the Life Sciences at an Urban Research University Peter Hoffmann, Matthew Gonderinger, Edward Kramkowski Wayne State University (WSU) is an urban research university with many first-generation students. Lacking prior exposure, many students see physics courses as of low relevance to their careers. The previous use of a physics curriculum with poor alignment to the life sciences acerbated this problem. Through an NSF-IUSE grant "Student Success through Evidence-based pedagogies" (SSTEP), of which the presenter is the PI, a team in the department of physics overhauled the physics sequence for life science students in 2015. The goal was fourfold: To increase relevance, to consistently introduce active learning strategies in lectures, discussion and labs, to improve student success and retention, and to create student interest in biomedical physics. I will report on the rationale, process, challenges, outcomes and future of this reform project, and how it fits into the context of institutional reform around student-centered teaching and broad use of evidence-based teaching methods. |
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H71.00054: INDUSTRIAL AND APPLIED PHYSICS
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H71.00055: Ideal memristor based on viscous magnetization dynamics driven by spin torque Guanxiong Chen, Sergei Urazhdin, Sergei Ivanov We use analytical calculations and simulations to show that ideal memristors - devices whose resistance is proportional to the charge that flows through them - can be realized using spin torque-driven viscous magnetization dynamics. The large damping required for the viscous dynamics can be achieved by utilizing the spin liquid state in F/AF heterostructures, where spin glass and spin liquid states emerge due to the frustration of exchange interaction [1,2]. The viscosity, and thus the memristive response, is tunable by proximity to the glass transition. |
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H71.00056: Additive manufacturing of highly reconfigurable plasmonic circuits for terahertz communications Yang Cao, kathirvel nallappan, hichem guerboukha, Guofu Xu, Maksim Skorobogatiy THz waveguide-based integrated solutions can be of great utility at both the transmitter and receiver ends, thus simplifying the miniaturization and mass production of THz communications systems. Here we present a type of modular THz integrated circuits based on the two-wire plasmonic waveguide components fabricated using a combination of stereolithography 3D printing, wet chemistry metal deposition, and hot stamping techniques. Particular attention is paid to the design of the optical circuits based on the two-wire waveguides suspended inside a protective micro-sized enclosure featuring low transmission and bending losses, as well as low dispersion. Using such waveguides as basic building blocks, we demonstrate several key optical components, such as low-loss broadband 2×1 THz couplers, waveguide Bragg gratings, and two-channel add-drop multiplexers that operate at 140 GHz. We believe that the reported micro-encapsulated two-wire waveguide-based modular platform can have a strong impact on the field of THz signal processing and sensing due to the ease of device fabrication and handling, high degree of reconfigurability, and high potential for real-time tunability. |
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H71.00057: A universal method for depositing patterned materials in-situ Yifan CHEN, Siu Fai HUNG, Sen YANG, Kangwei Xia Current techniques of patterned material deposition require separate steps for patterning |
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H71.00058: Thermo-optic tuning of optical loss in an optical micro-ring resonator for reconfigurable photonics Aneesh Dash, Viphretuo Mere, Shankar Kumar Selvaraja, Akshay K Naik Reconfigurable photonics is essential for next generation photonic signal processing and communication using photonic integrated circuits. The micro-ring resonator is an important building block in these systems. Conventional thermo-optic tuning used in photonic integrated circuits only tunes the resonant frequency, but not the quality factor and extinction ratio. Alternative methods such as electro-optic effect, all-optical effect, require complex fabrication and/or integration of foreign materials on conventional integrated-optic platforms such as silicon or silicon nitride. It is desirable to achieve full reconfigurability of the micro-ring resonator using the thermo-optic effect. We experimentally demonstrate this reconfigurability using a novel optical micro-ring resonator architecture. Thermo-optic tuning is used to tune the loss of the optical cavity, which leads to tuning of the quality factor (2000 to 10000) and extinction ratio (few dB to >30 dB). These devices are useful in reconfigurable switches and reconfigurable optical computing. |
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H71.00059: High-Performance Electronic Measurements of Protein Kinetics and Affinity Seulki Cho, Ryan Evans, Anthony J. Kearsley, Arvind Balijepalli We utilize high-performance field-effect transistors (FETs) for label-free biochemical measurements of both the affinity and kinetics of protein-ligand interactions. The kinetics of the inter-molecular interactions were extracted from a single time-course by leveraging a physical model of protein-ligand binding. This approach is in contrast to conventional measurements that often require multiple measurements at different ligand concentrations and can be hindered by the lack of adequate time-resolution. We demonstrate our approach using the biotin streptavidin model system. Thiol-modified biotin was conjugated to a gold surface to form a self-assembled monolayer (SAM). The interactions of streptavidin with the SAM were then measured dynamically. A mathematical model describes the physiochemical properties of the system and the time-evolved interaction between the proteins and ligands was fit to the time-series data and used to extract the rate constants as well as diffusion constant that characterize the interaction. Our results will enable the technique to broadly benefit biomolecular interactions of proteins with ligands, antibodies with antigens and numerous other systems to drive new applications in drug discovery and diagnostics of disease. |
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H71.00060: High spectral purity chip-scale tunable THz generation wenting wang, Ping-Keng Lu, Abhinav Kumar Vinod, James McMillan, mingbin yu, Dim-Lee Kwong, Mona Jarrahi, Chee Wei Wong High-Q nonlinear integrated resonators have emerged as a new platform which has been revolutionizing many fields in contexts such as optical frequency comb, laser spectroscopy and quantum-entangled sources. In this talk, we present the generation of tunable THz radiation with high spectral purity and broad frequency tunability. Mode splitting strength and position can be changed by controlling the pump-resonance effective detuning in a dispersion-managed Si3N4 microresonator through a differential thermo-optic effect. Therefore, tunable optical parametric oscillation can be observed by tuning pump-resonance detuning. A broadly tunable THz radiation from 0.3 THz to over 2.5 THz is generated after injecting the tunable parametric oscillation into a bias-free photomixer at room temperature. By feedback controlling the intracavity power of the microresonator, the radiated THz signal can provide a sub-Hz linewidth. Active intracavity power stabilization improves the long-term frequency stability by eight orders of magnitude reaching a record instrument-limited frequency residual instability of 6×10-15 in 1 second. The demonstrated chip scale tunable THz generation with high spectral purity can be used for frequency-domain THz spectroscopy. |
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H71.00061: Flexible Piezotronic Devices with Heterojunctions of 2D-Materials Sai Saraswathi Yarajena, Akshay K Naik Integrated sensor systems capable of detecting multiple physical parameters are important for application in wireless sensor networks, IoT (Internet of Things), wearable sensors, bio-implantable devices etc. 2D materials with inherent piezoelectric properties are an excellent candidate for such piezotronics devices. The electrical properties of these devices can be tuned using the inherent piezoelectric response. A heterojunction formed with piezotronics material can be used for improved strain sensing and also achieve switching behaviour. These are advantageous compared to simple resistive configuration devices in terms of better control over the charge carrier movement and switching action. The efficient design of these devices can make them self-powered. We have fabricated lateral heterostructures of MoS2 with other 2D materials such as MoTe2 and WSe2 on flexible substrates. We demonstrate the diode characteristics and response of these devices due to the strain. This study can be used to develop the stain gated transistors with heterojunctions of 2D materials. |
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H71.00062: Enhancing the thermoelectric efficiency of n-type half-Heusler compounds via self doping Parul Raghuvanshi, Dipanwita Bhattacharjee, Amrita Bhattacharya Ternary intermetallic XYZ half Heusler compounds (ZrNiSn, ZrPdSn, ZrCoSb) are promising thermoelectric compounds. The presence of a large number of tetrahedral voids in their structure as compared to the full Heusler stoichiometry (XY2Z) offers the possibility of off stoichiometric compositional tailoring. Existing studies have shown that small concentration of self-doping at Y site in 18-electron based half Heuslers leads to anomalous lowering in the kL while leading to suitable n-type doping of the materials. We explore the change in the electronic and thermal transport behaviour of ZrNi1+xSn, ZrPd1+xSn, and ZrCo1+xSb compounds (for x = 0, 0.03, 0.125, 0.5, 1) from the first principles perspective. Our calculations reveal that ultralow self-doping of the composition by Y site elements lead to the maximum positive impact in the transport coefficients (i.e. kL reduces by more than 60 %, while the electronic transport coefficients enhance by 10 - 20 %) . These increase the figure of merit of these compounds considerably. |
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H71.00063: Facile Synthesis of Carbon Nanomaterials Varun Gupta, Samir Iqbal We present an environmentally-friendly and rapid synthesis approach of highly porous carbon nanomaterial. The direct pyrolysis of the cane sugar was achieved in a hand-fabricated Teflon microchamber. Nanoscale porosity was obtained by in-step decompositions of household baking soda. The surface properties, elemental composition, and crystallinity of the nano-synthesized material were analyzed with field emission scanning electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction. The data showed in-step incorporation of carbon into high surface area nanospherical morphologies. The oxygen got reduced from the decomposition of sodium bicarbonate. The trapped oxygen was mainly contributed by sodium complex. If employed as an anode in sodium ion battery, such ions would not oxidize when intercalating during the charging. This process of pre-sodiation will be assisting to higher efficiency in the working of a sodium ion battery or even supercapacitors where the intercalation/deintercalation process is rapid. |
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H71.00064: Casimir Juggling Connor Hafen, Daniel Sheehan
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H71.00065: Surface Defect Engineering of MoS2 for Atomic Layer Deposition of TiO2 Films Yelda Kadioglu, Jaron A Kropp, Ankit Sharma, Wenjuan Zhu, Can Ataca, Theodosia Gougousi We studied thermal atomic layer deposition (ALD) of TiO2 from tetrakisdimethylaminotitanium (TDMAT) and trimethylaluminum (TMA) with H2O, combining experimental and computational approaches on MoS2 surfaces.Depositions on as produced chemical vapor deposition MoS2 flakes result in discontinuous films.Surface treatment with mercaptoethanol (ME) does not improve the surface coverage and DFT calculations show that ME reacts very weakly with the MoS2 surface.However,creation of sulfur vacancies on the MoS2 surface results in much improved surface coverage and the calculations show that TDMAT,TMA and ME react moderately with either single or extended sulfur vacancies.The computational studies however reveal that the creation of surface vacancies results in the introduction of gap states that may deteriorate the electronic properties.Treatment with ME results in the complete removal of the gap states originating from the most commonly found single vacancies and reduces substantially the density of states for double and line vacancies.As a result,we provide a pathway for the deposition of high-quality ALD dielectrics on the MoS2 surfaces,which is required for the successful integration of these 2D materials in functional devices. |
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H71.00066: Evanescent Field Polarization for Giant Chiroptical Modulation from Achiral Gold Half-Rings: Theoretical Insight from Simulations Luca Bursi, Lauren A. McCarthy, Kyle W. Smith, Alessandro Alabastri, Wei-Shun Chang, Peter Jan Arne Nordlander, Stephan Link Metal nanoantennas have been under intense investigation due to their strong light−matter interactions and significant polarization sensitivities determined by their structure. For applications seeking to realize on-chip polarization-discriminating nanoantennas, efficient energy conversion from surface waves to far-field radiation is desirable. However, the response of individual nanoantennas to the particular polarization states achievable in surface waves, such as evanescent fields, has not yet been thoroughly studied. |
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H71.00067: Routes towards the epitaxial integration of gallium oxide with silicon Tobias Hadamek, Agham Posadas, Fatima Al-Quaiti, David J Smith, Martha R McCartney, Alexander Demkov We report on the structural properties of Ga2O3 grown by plasma-assisted MBE on STO, STO-buffered Si (001) and gamma-alumina buffered Si (001). The integration of Ga2O3 with Si can lead to a lowering in cost of Ga2O3 wafer production, enable monolithically-integrated devices and gives the low-thermal conductivity material Ga2O3 a platform with higher thermal conductivity. The grown structures were investigated by XPS, RHEED, XRD, XRR and HRTEM. On STO (001) and STO-buffered Si (001), the growth planes (-112) and (100) of beta-Ga2O3 are observed, on gamma-alumina which takes the (111) orientation on Si (001) the (-201), (101) and (310) growth planes of beta-Ga2O3 are observed. Common theme that guides the epitaxial relationship is a matching of the (distorted) cubic centered oxygen sublattice of beta-Ga2O3 to the sublattice of the oxide (pseudo-)substrate. Since beta-Ga2O3 has a low symmetry monoclinic structure multiple in-plane orientations of the films are observed with respect to the substrate. |
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H71.00068: OUTREACH AND ENGAGING THE PUBLIC
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H71.00069: STEAM Program, engaging Youth in STEAM Magdalena Waleska Aldana Segura, Julián Felix-Valdez STEAM program is a multilevel intervention to promote awareness and science interest amongst youth and the general public. After 15 years of research and students follow up. It is a bilateral collaboration between Universidad de San Carlos de Guatemala and Universidad de Guanajuato. The program accompanies students from K-12 levels to the higher education stages to keep them engaged and promote better opportunities for them. |
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H71.00070: How to do Physics Outreach during the COVID Pandemic Dan Fauni, Keeran Ramanathan, Ryan Hess, Steven S Simpkins, Matthew Becker, Roberto Ramos The COVID pandemic has thrown cold water over many face-to-face events, including educational outreach in physics. I report on an educational physics outreach which our student chapter of the Society of Physics Students did to engage high school students. Communicating via Zoom and using primarily household materials such as garden hoses, vegetable oil, toy tops, laser pointers, we performed physics demonstrations of principles in hydrostatics, optics, and even made home-made lava lamps to an audience of high school students. I discuss the challenges of doing virtual outreach and outline suggestions and examples of delivering compelling physics outreach in effective but safe ways during this pandemic. |
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H71.00071: A Free Renewable Energy and Quantum Physics-based Summer Camp for Middle School Girls Roberto Ramos In 2019, the Physics Wonder Girls Program1 provided a free, novel, renewable energy and quantum physics-based immersion experience to two cohorts of middle school girls selected from a pool of high-performing students in the Philadelphia-New Jersey area. Campers came from diverse communities were introduced to renewable energy, took a crash course on solar cells, and then built and raced solar cars, and solar boats. They were taught quantum physics principles including how quantum devices such as the LED and solar cells work, how blackbody infrared radiation is produced and detected, energy storage, and how superconductors work. Campers compared the efficiencies of silicon cells versus organic solar cells, built solar cells based on dyes from raspberry fruit, and used a thermal imaging camera to audit heat leaks. They met women physicists engineers - including a quantum materials scientist, women food scientists who use optics in R&D, toured a local food company and presented demonstrations to a community of friends and teachers. I will also discuss ideas to incorporate quantum information education in the future. |
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H71.00072: PUBLIC POLICY
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H71.00073: Fukushima, Nuclear Waste and Risk Management as an Argument for Nuclear Energy Robert Hayes The common narrative that nuclear is not safe enough or that nuclear waste and cost are objective or conclusive statements against the use of nuclear energy will be evaluated. Assuming safe enough is when a nuclear accident like Fukushima has no measurable medical consequences will be argued to be insufficient in current common public discourse dispite the obvious benefits. The almost arbitrarily small amount of nuclear waste, its safety record or the cost benefit analysis considerations for nuclear energy in climage change or sustainability will also be evaluated and shown not to be in the common narrative as would be expected from a risk managment approach. The extent to which this has become ubiqutous will also be considered from the literature. |
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H71.00074: The Physics of History and Its Implications for Policy Daniel Seligson, Anne McCants Study, live long, and prosper! These imperatives motivate the UN's Human Development Index, a measure of a nation's economic performance that can, unlike GDP, distinguish between Japan and Equatorial Guinea. Though the mean of its distribution in 177 nations grows like e+t/70 between 1870 and 2020, the distribution's autocorrelation function decays like P(t)~e-t/625. If rich nations and poor differ because of the quality of their institutions, or if institutions rule, as the thrice-Nobel'd New Institutional Economics proclaims, then how can it be that the immense institutional change of these last 150 years has resulted in so little change in the distribution of wealth? |
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H71.00075: How to control nuclear weapons and make our world safer? Donald Chang Today, the entire mankind is living under the shadow of nuclear war. The stocks of nuclear weapons in US and Russia at present are more than enough to destroy all major cities in our world. How can we protect human from this nuclear threat? As a first step of nuclear armament control, we propose to revise the Treaty on the Non-Proliferation of Nuclear Weapons to add a new article, which specifies that all existing and future nuclear weapons will have two sets of launching codes. The first set of launching code will be controlled by the government owning those nuclear weapons, just like what is practiced today. The second set of launching code will be controlled by a new international body established by the United Nation. The launch of the nuclear weapon will require both sets of codes. That means, no government can launch any nuclear weapon unilaterally without the approval of the international body. This will be greatly helpful to prevent accidental nuclear war or nuclear blackmail. |
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H71.00076: ENERGY RESEARCH AND APPLICATIONS
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H71.00077: Dimethylamine Hydrochloride Passivated Perovskite Surface Towards Enhanced Solar Cell Performance Md Ashiqur Rahman Laskar, Nabin Ghimire, Qiquan Qiao Solution processed polycrystalline perovskite films surface frequently suffers from defects and charge traps especially in the grain boundaries (GB) deteriorating the overall device performance. In this work, for the first time we report Dimethylamine hydrochloride (DMH) as an effective passivating agent for perovskite surface in the inverted structure solar cell. When DMH (C2H7NHCl) is employed on MAPbI3 surface, it reduces defects and filled trap states in the perovskite GB. As a result, passivated MAPbI3 films possess smaller non-radiative recombination as supported by photoluminescence spectra. Besides, DMH passivated perovskite films exhibit higher surface current and less RMS roughness which are beneficial for good interfacial contact and efficient charge transportation. Consequently, photogenerated charge transport time is decreased after the passivation. Basically, DMH performs Pb-N coordination bonding with Pb2+ and deactivates the malefic under-coordinated Pb2+ on perovskite surface or GB which helps to improve the device performance. Eventually, the power conversion efficiency (η) jumps from 15.17% to 17.50% through the simultaneous improvement of short circuit current density (Jsc) and open circuit voltage (Voc) in the DMH passivated MAPbI3 perovskite solar cells. |
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H71.00078: Heterogeneous bilayer as an artificial solid-electrolyte-interphase for dendrite free lithium deposition in lithium metal batteries rajesh pathak Lithium metal anodes (LMAs) are considered promising for driving high energy density battery applications, owing to their higher theoretical specific capacity, lower mass density and lower redox potential, compared to conventional graphite based anode. Despite attractive features, the direct use of LMA challenges safety concern, and poor life span of the battery due to the inherent problems of infinite volume expansion, hyperactive nature, unstable solid electrolyte interphase (SEI) and undesired lithium dendrite growth. To resolve these issues, radio frequency (R-F) sputtering of ultrathin bilayer of graphite and SiO2 as an effective SEI layer on top of LMA chip was illustrated. As a result, dendrite-free uniform Li deposition, stable voltage profile and outstanding Li plating/stripping was achieved compared to that of bare LMA. Electrical conductive graphite electrically connect the plated Li and bulk LMA, lowers the impedance, buffers the volume expansion during Li plating/stripping and reduces the chances of dead Li formation. The addition of SiO2 facilitates fast Li-ion diffusion and simultaneously stores Li by alloying mechanism. As a result, outstanding electrochemical battery performance was obtained using hetereogeneous bilayer deposited LMA. |
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H71.00079: Sublattice mixing in Cs2AgInCl6 for enhanced optical properties: High-throughput screening from first-principles Manish Kumar, Saswata Bhattacharya A stable and non-toxic double perovskite (Cs2AgInCl6) has been reported as an alternative to lead halide perovskites APbX3 (A = CH3NH3+, HC(NH2)2+, Cs+, and X = Cl−, Br−, I−) in the field of optoelectronics. However, due to the wide bandgap (3.3 eV), it doesn’t show an optical response in the visible region. Therefore, we report here the tuning of its bandgap via sublattice mixing (partial substitution of several metals M(I), M(II), M(III) at Ag and/or In sites) and enhancing its optical properties. Here we have employed high-throughput screening using a hierarchical first-principles based approach starting from density functional theory (DFT) with appropriate exchange-correlation functionals to beyond DFT methods under the framework of many-body perturbation theory (viz. G0W0@HSE06). Our results reveal that substitution of Co2+, Ni2+, and Cu2+ is thermodynamically unstable and these can decompose into ternary compounds. We have also inferred that the sublattices with Cu+ and Au+ at Ag site, Ir3+ at In site, Zn2+ and Mn2+ at Ag and In site simultaneously, as the most promising candidates for various optoelectronic devices under visible light. |
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H71.00080: Tuning electronic and optical properties by sublattice mixing of Cs2AgBiCl6 for solar cell application: High-throughput screening from first-principles. Deepika Gill, Saswata Bhattacharya The lead-free double perovskite material (viz. Cs2AgBiCl6 ) has emerged as an efficient and environmentally friendly alternative to organic-inorganic hybrid lead halide perovskites. However, Cs2AgBiCl6 is optically inactive in the visible region owing to its large indirect band gap. To make Cs2AgBiCl6 optically active in the visible region of the solar spectrum, band gap engineering approach has been undertaken. Using Cs2AgBiCl6 as a host, bandgap and optical properties of Cs2AgBiCl6 have been modulated by alloying with M(I), M(II), and M(III) cations at Ag-/Bi-sites. Here, we have employed density functional theory (DFT) with suitable exchange-correlation functionals in light of spin-orbit coupling (SOC) to determine the stability, band gap, and optical properties of different compositions, that are obtained on Ag-Cl and Bi-Cl sublattices mixing. On analyzing 64 combinations within Cs2AgBiCl6, we have identified 19 promising configurations having band gap optimum to solar cell applications. The most suitable configurations with Ge(II) and Sn(II) substitutions have spectroscopic limited maximum efficiency (SLME) of 32.08% and 30.91%, respectively, which are apt for solar cell absorber. |
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H71.00081: Role of defects in MAPbI3 to modulate optical absorption and solar cell efficiency Pooja Basera, Saswata Bhattacharya Methylammonium lead halide (MAPbI3) perovskite has emerged as one of the frontier optoelectronic semiconductors. To avoid lead toxicity, the role of Sn substitution and Pb vacancy (Pb-■) are addressed in regulating the stability and solar cell efficiency of MAPb1−X−YSnX■YI3 perovskite using hybrid density functional theory (DFT). The role of spin-orbit coupling (SOC) and the electron's self-interaction error are examined carefully. We find to reduce the Pb content from pristine MAPbI3, Sn substitution has a more favorable thermodynamic stability than creating Pb-■. Moreover, on substituting Sn, due to strong s−p and p−p couplings, the lower parts of the conduction band gets shifted downwards, which results in the reduction of the bandgap (direct). This further helps us to get a high optical absorption coefficient (redshifted) and maximum solar cell efficiency in MAPb1−XSnXI3 for 0<X≤0.5. |
(Author Not Attending)
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H71.00082: Adavanced First-Principles Modeling of Electrocatalysis at Solid-Water Interface Xunhua Zhao, Yuanyue Liu Kinetic information, such as the activation energy and transition state, is critical to understanding the reaction. However, the kinetic information of electrochemistry at solid-water interface is challenging to obtain from conventional models of density functional theory (DFT), as they often neglect the presence and/or the dynamics of the surface charge [1] and the solvent configuration, which are further coupled. Here we present a new model that accounts for these effects, by combining hybrid solvation, constant-electron-potential, and slow-growth sampling techniques together. We then apply this model to elucidate the active site structure and the mechanism of electrochemical carbon dioxide reduction catalyzed by single-nickel-atom embedded in graphene, which shows high performance in experiments while is not well understood [2]. |
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H71.00083: Structural dynamics and transport in deep eutectic solvents Stephanie Spittle, Derrick Poe, Benworth Hansen, Yong Zhang, Edward Maginn, Joshua Sangoro Non-aqueous solvents that are scalable, easy to prepare and functionalize are needed in many applications, especially energy storage. Deep eutectic solvents (DESs) present a large design space and are therefore tunable, in principle, for such targeted applications. To understand the correlation between local structure and macroscopic dynamics, detailed studies of model DESs were carried out utilizing a wide range of techniques, including classical molecular dynamics, broadband dielectric, nuclear magnetic resonance, dynamic mechanical and femtosecond transient absorption spectroscopy, and differential scanning calorimetry. The evolution of the local structure in varying compositions of hydrogen bond donor (HBD) to hydrogen bond acceptor (HBA) is studied from molecular to macroscopic length-scales. We find that the microscopic heterogeneities induced in the HBD by the addition of the HBA lead to new slow, dynamic modes that are absent in the HBD. These results provide a unified framework for rationalizing the key features of DESs including a decrease in the glass transition temperature, corresponding to an increase in dc ionic conductivity, fluidity, diffusivity, and the mean rates of orientational dynamics in the vicinity of the eutectic composition. |
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H71.00084: Thermodynamic Transitions and Dynamics in Model Systems of Deep Eutectic Solvents Benworth Hansen, Stephanie Spittle, Joshua Sangoro The impact of composition on the thermodynamic transitions and dynamics in model systems of deep eutectic mixtures is investigated by broadband dielectric spectroscopy and differential scanning spectroscopy, complemented by NMR and vibrational spectroscopy. It is found that non-eutectic compositions exhibit rich phase behavior characterized by solidus and liquidus transitions in addition to the melting and/or glass transitions found in their eutectic counterparts. The role of structural heterogeneity in determining dynamics in deep eutectic mixtures will be discussed within the framework of recent models of the glass transition. |
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H71.00085: Morphology control by optimizing process conditions for efficient wide-bandgap perovskite solar cells Khan Mamun Reza, Abdullah Al Maruf, Yue Zhou, Quinn Qiao, Brian Logue Efficient wide-bandgap perovskite is essential to construct the tandem structure to achieve efficiency beyond the Shockley-Queisser limit of single-junction solar cells. But the performance of wide-bandgap perovskites is mostly limited by the defects in the Br-rich active layer. Morphology, especially the grain boundaries, roughness, unreacted lead halides, etc. play important role in regulating the defects. Here, we report an efficient way to control the morphology and properties of the perovskite by adjusting process temperature (glove box temperature) during crystallization and tailoring the annealing process. It was observed that GB temperature maintained at ~27 °C with a delay before annealing results in bigger grains and less unreacted lead halides with a more uniform and smoother perovskite film, which results in reduced defects and better charge transport properties. The synergy of these two led to an efficiency of 15.68% for 1.78 eV perovskite solar cells compared to 12.53% of that without adjustment of the process conditions. The findings of this work offer a new window to optimize the morphology of the perovskite for higher efficiency and stability. |
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H71.00086: Simulations of Argon Plasma Decay in a Thermionic Converter Roelof Groenewald, Stephen E Clark, Arvind Kannan, Peter Scherpelz Thermionic generators convert heat to electricity with no moving parts. Thermionics comprise an electron emitting cathode and an electron collecting anode separated by a vacuum gap. Typically, a plasma is used to mitigate space charge. Here, we report on a comprehensive modeling effort of the dynamics of an argon plasma in the gap of a thermionic diode. We applied particle-in-cell simulations to characterize the time averaged diode current, as a function of the relative electrical potential between the electrodes, while the plasma density depletes due to recombination on the electrode surfaces. Simulations were performed in 1D and 2D and significant differences were observed in the plasma decay between the two cases. Specifically, in 2D, well defined plasma sheaths formed in front of both electrodes, while in 1D the sheath heights varied continuously. This creates significant differences in the time averaged diode current. In 2D simulations, the maximum time averaged current is collected when the diode voltage is set to the so-called flat-band condition, i.e. where the cathode and anode vacuum biases are equal. This suggests a novel technique of measuring the difference in work-functions between the cathode and anode in a thermionic converter. |
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H71.00087: Ferrofluid-Based Generator Harvesting Waste Heat and Ambient Vibration Xuewei Zhang Ferrifluid is a stable colloidal suspension of permanently magnetized nanoparticles, in which Brownian motion keeps the nanoparticles from settling under gravity, and a surfactant is placed around each particle to provide short range steric repulsion between particles to prevent agglomeration. Since magnetic field device has no limitations analogous to electrical breakdown in its electric field counterpart, ferrofluids have become an excellent choice for micro-/nanoelectromechanical systems technology. On the other hand, ferrofluids have applications in the cooling of electronic devices, which has led to several designs of power generators using waste heat. In this work, we study a new version of ferrofluid generator harvesting both heat and vibration energy. A theoretical model based on fundamental physics principles is developed to evaluate the system's energy conversion efficiency (the ratio of generated power and the heat input). Further, we discuss the dependence of the output power on various design parameters (including the scale of the system) and methods to enhance the performance of the ferrofluid generator or potential aerospace applications. |
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H71.00088: Frustrated Lewis Pairs with Applications in Hydrogen Storage Glory Russell-Parks, Brian Trewyn, Thomas Gennett Due to the abundance and large gravimetric energy density, hydrogen has been considered a potential source of energy.1 However, major challenges associated with utilizing hydrogen for energy include efficient and safe storage and transportation of it. Frustrated Lewis pairs (FLPs) have recently proven their importance in hydrogen storage applications.2 In contrast to classic Lewis acid-base pairs, functionalizing the acid and base to contain bulky ligands prevents them from binding to their counterpart causing them to be in a “frustrated” state.3 The acid and base are held together by weak intermolecular forces without neutralization, which allows small molecules such as hydrogen to weakly bond to the Lewis acid and base in a heterolytic mechanism. Catalytic systems that utilize FLPs may assist with lowering the sorption temperature and pressure, reducing the activation energy barrier and potentially allow for hydrogenation and dehydrogenation to occur. This work focuses on the novel synthesis and characterization of an FLP system. |
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H71.00089: Characterization of Casein Synthesized by Protonation with organic and inorganic acids Tharika Senevirathne, Gimhani Wickramasinghe, Susira Perera Casein is the dominant protein in cow’s milk .The pH value of milk is 6.6 where casein has a negative charge to prevent its coagulation.By gaining protons, casein reaches to its isoelectric point (pH 4.6) where it coagulates to produce a solid precipitate.The casein was prepared by reducing the pH introducing organic and inorganic acids to heated skim milk. As organic acids, acetic, lactic, formic and ascorbic were used and H3PO4, H2SO4 and HNO3 were used as the inorganic acids. The casein obtained with different acids was washed and dried. A paste was made by ball milling aforementioned casein with distilled water. This paste was used to cast thin films on conducting glass by doctor blade method.The films were characterized with the Mott-Schottky measurements(MS) and UV-Visible spectroscopy. Significance difference could not be seen with the above measurements depending on the acid used to prepare casein. The MS analysis revealed that casein has n-type conductivity where its conduction band lies at - 0.61V with respect to the Ag/AgCl electrode. Band gap of casein found to be 3.9 eV that calculated from tauc plot .The results indicated that casein is a good insulating material, but further studies are ongoing to tune its conductivity for applications in optoelectronic devices. |
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H71.00090: Protective solid-electrolyte-interphase for dendrite-free stable lithium metal batteries LITON KUMAR BISWAS, Rajesh Pathak, Yue Zhou Lithium (Li) is considered the most promising anode material in Li metal batteries (LMBs) owing to its high theoretical capacity. However, the formation of unstable solid electrolyte interphase (SEI) layer and unexpected Li dendrites growth during electrochemical deposition leads to lower cycling performance and coulombic efficiency with a safety concern, which have hindered the real-world applications of rechargeable LIBs. Here, we develop a facile and efficient approach to overcome these issues. An ultrathin Nickel (Ni) layer (50nm) has been sputtered on the surface of Li chips in a nitrogen environment to obtain a protective artificial SEI layer comprising of Li3N and Ni3N. Lithiophilicity, and higher ionic conductivity (4.9×10-1 mScm-1) of Li3N and Ni3N prevent the direct contact between extensive reactive Li metal and liquid electrolyte, which promote homogeneous deposition of Li, suppression of Li dendrites formation, and improvement of Li-ion diffusion. Besides, Ni performs as an electrical bridge between Li metal electrode and the plated Li, which promotes lowering the impedance. In a symmetrical cell, this artificial SEI layer exhibits a stable voltage profile with excellent plating/striping cycles compared to bare Li anode. |
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H71.00091: The Effect of Strain on Vibrations in Cubic CsPbI3 Perovskite Nicholas Lopez, Kuntal Talit, David A Strubbe Cubic CsPbI3 is an inorganic halide perovskite that is being explored for highly efficient and stable solar cells. Studies into lead perovskite materials have grown exponentially over the last decade due to their rapid increase in power conversion efficiency growing from 3.8% in 2009 to 25.2% in 2020.This project is a computational study using Density Functional Theory (DFT) aimed at determining how the vibrations change with strain. We found the optimized structure using different functionals (PBE, LDA, and PBEsol) to be in good agreement with experiment, and found that the band structures differed mainly by a constant vertical shift. Phonon calculations were carried out for the unstrained structure, and imaginary frequencies and structural instabilities were investigated for the cubic structure of CsPbI3. We then computed how phonon frequencies changed because of strain. Due to the symmetry, there are Raman-active modes only when Cs is off-centered. Consequently, we investigated how IR-active frequencies changed due to strain, which can allow measurement of strain with IR spectroscopy. Ultimately, this project will provide more insight into perovskite materials that can be used to further increase efficiency in solar panels. |
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H71.00092: Migration barrier assisted oxygen redox stability in NMO cathode Kuan-Hsiang Hsu, Iwnetim I Abate, C Das Pemmaraju, Thomas Devereaux Designing a battery that has high energy density and high reversibility remains a challenge in modern research. For example, oxygen-redox active cathodes provide a promise for higher capacity than conventional cathodes, such as LiCoO2, but are prone to voltage hysteresis and capacity fading during charging cycles. However, a recent study showed an exceptional reversibility and low-voltage hysteresis of oxygen-redox active cathode, Na2Mn3O7 (NMO) (Mortemard de Boisse et al., 2018). In this work, we utilize ground state and excited state calculation to determine the redox mechanism of NMO that enabled in the low voltage hysteresis of the cathode. The results provide insight into NMO defect structures that are unfavorable kinetically but can be detrimental to the stability of the NMO cathode material. |
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H71.00093: Role of Magnetic Field on Supercapacitive Properties of Electrospun NiCo2O4 Nanofiber Milan Singh, Asit Sahoo, K L Yadav, Yogesh Sharma The ever-growing demand for high power and energy density in electrical vehicles has triggered an interest in the development of supercapacitor due to its long cyclibility, high power density and environment friendly nature. Recently, effect of magnetic field on electrochemical performance of magnetic material has attracted much attention due to its great impact on improving capacitive performance. To understand the effect of magnetic field on supercapacitive performance of NiCo2O4 (Ni-Co) nanofiber, it has been first fabricated by electrospinning technique and then the material is characterized by TGA, XRD, FE-SEM and BET. The magnetic properties of Ni-Co has also been evaluated. The electrochemical measurements like cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) have been performed in 2M KOH electrolyte solution in the presence/absence of 3 mT external magnetic field. In the presence of 3 mT magnetic field, Ni-Co nanofiber displays a change in capacitance value from 245 F g-1 to 270 F g-1 at 0.25 A g-1. A number of studies have been carried out to understand this change in supercapacitive properties. The results will be discussed in detail at the time of presentation. |
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H71.00094: Spin-orbit torque rectifier for energy harvesting from weak radio-frequency Shehrin Sayed, Sayeef Salahuddin, Eli Yablonovitch We will discuss a new application of materials exhibiting spin-orbit torque, especially in radio detection, and particularly for harvesting ambient weak radio signals, where conventional technologies fail to operate. We propose a rectifier concept, simultaneously utilizing the spin-orbit torque and the Hall effect, that can provide 100 μV DC voltage from a 500 nW of radio-frequency (RF) power using existing materials, with a power conversion efficiency as high as 71%. The DC voltage strength can be efficiently enhanced to 100 mV from the same RF power with a series array of such devices while matching the low impedance of the receiver antenna. The Hall effect and spin-orbit-torque are both proportional to current density, which improves inversely with device cross-sectional area, providing the largest signals at the nanoscale. The proposed device can lead to important new technologies addressing the alarming energy issues in the era of the internet-of-things, wearable devices, and densely integrated 3D circuits. |
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H71.00095: Green energy generation by splitting water from nanoporous NiFe2O4 based Hydroelectric cell SANDEEP SAINI, K. L. Yadav, Jyoti Shah, R. K. Kotnala Renewable energy is the driving wheel for future technologies. Due to the limited stock of fossil fuels and their environmental impact, there is an ever-increasing demand for clean energy sources. Hydroelectric Cell (HEC) is one of the excellent tools which produce green energy. In the device fabrication of HEC, a Zn plate has been used as anode, Ag paste as a cathode, and the material as the electrolyte. In this direction, we synthesized a nanoporous NiFe2O4 using the solid-state reaction method. NiFe2O4 pellets were sintered at two different temperatures, 950 and 1050 °C, for two hours. It was found out that the maximum current output of NiFe2O4 based HEC decreases with an increase in the sintering temperature (leads to grain growth). This grain growth reduces nano-porosity and the number of defects in the material, which are the vital parameters for the separation of physisorbed water molecules. The V-I polarisation curve of NiFe2O4 based HECs provides a maximum current output of 15.3 mA for the samples sintered at 950 °C, and 9.28 mA for the ones sintered at 1050 °C. Variation in Oxygen vacancies with sintering temperature was analyzed after the peak fitting of O1s spectra, which was obtained from the X-ray Photoelectron Spectroscopy. |
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H71.00096: Transport Properties of Combustion Derived Na2MnSiO4 HARISHPAL HARISHPAL, Yogesh Sharma Na2MnSiO4 (NMS) has been considered a promising cathode material for Na+ battery. Importantly, the electrochemical performance of NMS cathode material is directly correlated with the transport behavior of Na+ into the bulk of NMS crystal. Herein, the bulk transport properties of monoclinic-NMS, synthesized by the urea combustion method, are investigated by AC electrochemical impedance spectroscopy (EIS) and I-V measurement techniques at room temperature for the first time. The impedance response recorded in the frequency range of 10mHz-1MHz shows a depressed semicircle that suggests the bulk contribution to the resistance. The AC conductivity of NMS is found to be 6.5(±0.5) × 10-7 S cm-1 whereas DC conductivity is calculated to be 5.8(±0.5) × 10-8 S cm-1. |
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H71.00097: Correlation between Li-ion migration and local structural distortion in Li superionic conductors Runxin Ouyang, Ronghan Chen, Zhenming Xu, Hong Zhu The all-solid-state Li-ion batteries, overcoming the shortages of liquid electrolyte, have emerged to be promising for the next-generation energy storage system, where the development of new solid-state electrolytes (SSE) with high ionic conductivity is critical. In this study, we aim to reveal the correlation between activation energy barriers, volume, local structural distortion (characterized by continuous symmetric measure, CSM) of the migrating Li-ions by first-principles calculations. Three typical superionic conductor systems, Li3MX6 (M= La, Sc, Y, X= Cl, I, Br), garnet Li7La3Zr2O12, and Li10XP2S12 (X = Ge, Si, Sn) are studied. By analyzing the energy barrier, CSM, and local volume of migrating Li-ion along different paths, we note that the Li site with smaller volume is usually accompanied by higher structural distortion, whose site energy is also more sensitive to the variation of structural distortion. Thus, for the Li migration involving tetrahedral and octahedral sites, it is more effective to tune the tetrahedral site's structural distortion to achieve low activation energy, e.g. reducing the tetrahedral transition Li site distortion or increasing the tetrahedral initial Li site distortion. |
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H71.00098: High-throughput screening of ion adsorption and diffusion on Sulfur-functionalized MXenes for battery electrode applications Gracie Chaney, Deniz Cakir, Can Ataca Two-dimensional materials composed of transition metal carbides and nitrides (MXenes) are poised to revolutionize energy conversion and storage. MXenes exhibit the high capacity needed for electrodes in ion batteries and the high-power rate needed for supercapacitors. Also, it has been shown that adding Sulfur terminations decreases diffusion barrier for some ions. In this work, we tested adsorption of various adatoms (Ca, Mg, Na, Al, and Zn) on nine CM2S2 monolayers (M: Cr, Hf, Mo, Nb, Ta, Ti, V, W, Zr). We found that Ca binds the most strongly to all of the MXenes, and that Zn binds the weakest in dilute concentrations. Due to the thickness of CM2S2 layers, adatom-adatom interactions are screened in double-sided ion adsorption. In addition to these, we conducted cluster expansion simulations in order to study coverage dependent adsorption energies and open-circuit operating voltages (OCV). For the adatom having positive OCV, the migration of adatoms across the monolayers are studied with nudge elastic band method. This work searches for possible ion candidates to be used on sulfur-functionalized MXene layered materials to be used for battery electrode applications and will be terminal work on battery applications of two dimensional materials. |
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H71.00099: INSTRUMENTATION AND MEASUREMENT SCIENCE
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H71.00100: FPGA Programming of Tunnable Waveform Generator Ben Rogers, Oleksiy Vasily Svitelski Field Programmable Gate Arrays are capable of accomplishing the goals of manufactured circuits while being able to be reconfigured in real time. One of the highlights to FPGA programming is the ability of executing commands in parallel as opposed to serial due to the hardware description nature of the code. Applications for FPGAs can be found in emulation of computer hardware, medical imaging, bioinformatics, and Digital Signal Processing. An example of signal processing is in the design of a tunable waveform generator capable of outputting sine waveforms up to 100 MHz and tuning amount of 0.5 Hz in either direction. Such a generator can be used in the simulation of lasers and laser control. Using the Xilinx Direct Digital Synthesis (DSS) IP, this is made possible. By using a reference clock of 268.75 MHz and a data word length of 29 bits, the tuning amount of 0.5 Hz can be obtained with minimal error while obeying the Nyquist sampling theorem. The data word length can also be increased for a more accurate tuning of up to 0.125 Hz in either direction. To improve on the design in the future, a digital Frequency Impulse Response filter can be created and configured to filter unwanted higher frequencies. |
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H71.00101: A scanning quantum cryogenic atom microscope at 6 K Stephen Taylor, Fan Yang, Brandon A Freudenstein, Benjamin L Lev The Scanning Quantum Cryogenic Atom Microscope (SQCRAMscope) is a quantum sensor in which a quasi-1D quantum gas images electromagnetic fields emitted from a nearby sample. We report improvements to the microscope. Cryogen usage is reduced by replacing the liquid cryostat with a closed-cycle system and modified cold finger, and cryogenic cooling is enhanced by adding a radiation shield. The minimum accessible sample temperature is reduced from 35 K to 5.8 K while maintaining low sample vibrations. A new sample mount is easier to exchange, and quantum gas preparation is streamlined. |
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H71.00102: Methodology for Focality Homogenization in Magnetic Stimulation of Biological Tissues Ivan Carmona, David C Jiles, Magundappa Hadimani Transcranial Magnetic Stimulation (TMS) is a type of neuromodulation used to regulate the neuronal activity to treat several brain disorders. In TMS, E-fields are induced by time-varying B-fields using coils from outside the head. Different definitions are found in the literature for the E-field focality in TMS [1-5], most of them with different measurement methodologies. Another common finding is definitions of “focality” without target area and/or focal distance, which are intrinsically related. Furthermore, to evaluate the degree of magnetic stimulation, a criterion indicating how well the stimulated area overlaps the targeted area is required. This work proposes a function and methodology for focality quantification considering target area, focal distance, peak value and stimulation threshold. New definitions describe the suitability of coils for specific stimulation applications and offer a general framework for comparison under homogeneous methodology, parameters and nomenclature. |
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H71.00103: Capillary Condensation in Peak Force AFM Imaging of Nanopores Sanket Jugade, Sohini Pal, Manoj M Varma, Akshay K Naik Capillary condensation in nano-confinements between two surfaces is a common phenomenon in micro-nano systems [1]. Based on the Kelvin equation, the length scale for capillary condensation in cylindrical nanopores is less than 3 nm [2]. Here we fabricated conical nanopores of avg. dia. 30 nm on a 100 nm thick silicon nitride film and performed Peak Force Imaging in AFM in air using a sharp silicon nitride tip. As the AFM tip scans the nanopore, the small gap between the periphery of the tip and walls of the conical pore leads to capillary condensation. Increasing the peak force should reduce the gap and increase the area of condensation on the tip. Therefore, increasing the peak force from 420 pN to 8.4 nN, increases the adhesion of tip-nanopore from 5 nN to 10 nN and the adhesion force profile also broadens. In contrast, the adhesion of tip-flat SiN substrate remains constant at 1.7 nN. We also performed imaging of nanopores for relative humidity values varying from 57% to 97%, for which the measured adhesion profile resembled that corresponding to the increasing peak force setpoint. These AFM measurements allow us to study capillary condensation even in much larger nanostructures. |
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H71.00104: Innovative ultra-low temperature thermometry guided by numerical simulations. Alexander Donald, Lucia Steinke, Andrew Woods Ultra-low temperature (ULT) measurements below 1 mK present a difficult challenge, especially in the presence of high magnetic fields B. We are working on developing novel ULT thermometry in order to meet User demand at the NHMFL High B/T Facility. For example, specific heat and thermal transport experiments at ULT and high B - particularly on small crystals or nanostructures – are essential to studies of quantum criticality, superconductors with very low transition temperatures, or to provide evidence for a quantum spin liquid state. To enable rapid measurements of small samples, we are simultaneously working on optimization of existing thermometers and development of thermodynamic simulations to predict thermometer warmup curves without the need to wait for full thermalization. In addition, we can use these simulation techniques to guide more efficient experiment design. I will talk about the development and use of these simulations. |
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H71.00105: Progress Toward Low Temperature Spin Hall STM Measurements Joseph Murray, Robert E Butera, Michael Dreyer The Spin-Hall effect has been observed1 in room-temperature polycrystalline tungsten films through scanning tunneling microscope (STM) measurements with both tungsten and iron-coated tungsten tips. When a lateral current is passed through the film, spin-polarized electrons accumulate on the surface which creates an asymmetry in the tunneling current with respect to the polarity of the sample bias. Furthermore, the use of an iron-coated tip results in an additional asymmetry which depends on the direction of the lateral current flow. We seek to extend these observations to topological insulators such as Bi2Se3 and PbSnTe under cryogenic conditions. We have implemented a new sample holder design for our low-temperature (4 K) STM, and are in the process of upgrading our system to operate at 1 K. This opens the door to performing dI/dV spectroscopy on spin-polarized topological materials as well as measuring atomic-scale lateral variations in the spin current. |
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H71.00106: Exploiting the Quantum Entangled State between Muon Spin and 51V Nuclear Spin (I = 7/2) in A15 Compounds by using Muon Spin Spectroscopy Jonathan Frassineti, Pietro Bonfà, Muhammad Maikudi Isah, Ifeanyi John Onuorah, Roberto De Renzi, Pascal Lejay, Vesna Mitrovic, Franz Lang, Stephen Blundell, Samuele Sanna We study the quantum interaction between the muon spin (S = 1/2) and nuclei with spin I > 1/2 and with electric quadrupole moment Q. It is well known that muon μ can form a quantum entangled state when implanted between two nuclear spins I = 1/2 (Q=0), which give rise to coherent oscillations in the μ spin polarization function measured by muon spectroscopy, e.g. in F-μ-F [1, 2]. We have recently observed coherent oscillations of the μ polarization in the V3Si system with A15 structure. A correct description for large nuclear spin I = 7/2 of 51V should include also the quadrupolar interaction. We have developed an open-source program, UNDI [3], to simulate the muon spin polarization function by both exact and approximated estimates in presence of dipolar and quadrupolar interactions. By comparing the experimental and simulated results we provide a detailed description of the quantum V-μ-V interaction. The results suggest that this interaction might be informative about charge and structural related phenomenon occurring in quantum materials by using muon spin spectroscopy. |
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H71.00107: Ultrathin metasurface 12 GHz microwave parabolic reflector Abdur Rahman, Sinhara Silva, Abul K. Azad This work demonstrates a thin, light-weight, low cost, and easily deployable flat metasurface reflector consisting of radially symmetric subwavelength sized resonators operating at 12 GHz. The resonators are designed using variable-sized patches with pre-defined phases between 0 to . The planar resonator array introduced a desired parabolic phase variations from 0 to ~2.0from the center to the edge of the reflector. It achieved a parabolic mirror-like reflection profile at a focal length of 50 cm along the axis through the metsurface plane's center. The reflector exhibits 16dBi gain enhancement at 11.8 GHz and a 3dB directionality < 50 while fed by a horn antenna. |
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H71.00108: Quantifying the probing depth of mode-synthesizing atomic force microscopy for nanoscale infrared spectroscopy Fernand Torres-Davila, Chance Barrett, Laurene Tetard Advances at the forefront of nanoscale infrared spectroscopy have deepened our fundamental understanding of heterogeneous materials and living systems at the nanoscale. By combining the nanomechanical detection scheme of atomic force microscopy (AFM) and infrared excitation, local properties can be resolved with spatial resolution in the sub-100nm range. However, the complexity of the probing depth contributing to the signal is one of the limitations hampering thr full exploitation of this approach. |
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H71.00109: MEDICAL PHYSICS
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H71.00110: NMR detection of cancer: Mechanism of contrast generation Donald Chang One of the most effective ways today to detect cancer is using MRI (Magnetic Resonance Imaging). This technique is based on the nuclear magnetic resonance (NMR) measurement of water hydrogen signal inside the human body. In order to detect cancers using the NMR method, one needs to solve two technical problems: (1) How to produce a contrast between water molecules inside the cell and the extra-cellular water? (2) How to differentiate the water signals in cancer cells from the water signal in normal cells? These difficulties were resolved in the early 1970s through the discovery that the relaxation times of water protons inside the cells were very different from those of the extra-cellular water. Furthermore, we discovered that the relaxation times of water molecules undertake a progressive lengthening during the transformation from normal cells to cancer cells. In this presentation, I will give a concise review of the evidence for these discoveries. Finally, I will discuss the possible physical basis that may account for the relaxation time changes between normal cells and cancer cells. |
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H71.00111: Characterization of Breast Phantom Models in Coaxial Probe Ali Raza, Thiago campos, LORENNA KARYNNE BEZERRA SANTOS, Saher Jabeen, Muhammad Arshad Kamran, Maryam Liaqat Breast cancer is a major problem of public health worldwide. The main tool in reducing the death rate from this disease is early diagnosis. Despite the widespread use of mammography, it has some disadvantages in its use as direct patient exposure to ionizing radiation; the similarity in density between tumor and the normal tissues; and low reproducibility in highdensity breasts. The positron breast microwave (MWT) is a very promising alternative to help diagnose breast cancer. This tomography technique has some advantages, greater ease in early diagnosis and difficult location, less exposure of the patient; lower cost; and greater comfort to the patient. It is necessary for the production of phantoms with similar characteristics to human tissue, for the use of MWT in breasts. This work has as main objective the development of a specific breast phantom tomography in microwave and characterization through simulations and measurements in open coaxial probe. The simulation results (using HFSS software) and experimental measurements of phantoms in coaxial probe were consistent with the literature. Given the results, it is expected that the characterization of the research phantoms contributes positively to the consolidation of MWT. |
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H71.00112: Virus Host Receptor Adhesion Suresh Ahuja Viral infection involves a large number of protein-protein interactions (PPIs) between virus and its host. The complex process of metastasis involves the formation of migratory cells, the so called epithelial mesenchymal transition (EMT), which enables cancer cells to break loose from the primary tumor mass and to enter the bloodstream. To break loose from the primary cancer, cancer cells have to down-regulate the cell-to-cell adhesion molecuIes(CAMs) which keep them attached to neighboring cancer cells. Viruses are nanoscale entities containing a nucleic acid genome encased in a protein shell called a capsid and in some cases are surrounded by a lipid bilayer membrane. As part of their entry and infection, viruses interact with specific receptor molecules expressed on the surface of target cells, Dominant forces acting at the nanoscale between nanoparticles are the electrostatic forces and the Van der Waals forces. Cell .Virus interaction can involve non-bonded interactions (electrostatic, Van der Waals, hydrophobic) compared to hydrogen bonding between the proteins (PPI results in higher flexibility in the backbone of a virus that allows it to move closer to the human receptor protein surface, and to bind stronger to the receptor (using non-bonded interactions). |
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H71.00113: A model of leukocytes (White Blood Cells) Aggregation Suresh Ahuja Cell-cell interactions and cell-extracellular matrix (ECM) interactions affect immune regulation such as leukocyte trafficking via blood and lymphatic vascular system. The leukocytes has numerous folds which probably allows cell deformation without a change in surface area and volume. Leukocytes stiffness rigidity is largely determined by the cytoskeleton of actins and actins-binding protein and its degree of cross linking. White blood cells have a larger volume than red cells leading to the resistance imposed by a single white cell in capillaries is much larger than that of a single red cell. As large number of leukocytes move at a wide range of speeds, collisions occur. These collisions result in abrupt changes in the motion and appearance of leukocytes. The formation of adhesive bonds depends on local velocity and shear forces to the captured cells. Migration of leukocytes in blood flow and collision with vessel wall depends on the direct hemodynamic interaction of leukocytes with erythrocytes results in pushing leukocytes against the endothelium. A collision model between leukocyte and erythrocyte is presented where leukocyte being adhered to endothelium as shear stress and surface energy increases. |
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H71.00114: A novel approach to registration of RGB images of human hands Luka Rogelj, Jaka Ostrovršnik, Matija Tomsic, Matija Milanic, Urban Simoncic Spatial normalization permits pixel-level image comparison and analysis. It is used for the analysis of images of the same patient at different time points as well as different patients, imaged with the same or different imaging modalities. The method, mostly used on brain images, shows potential for its use on other body parts. Applying it to human hands could facilitate monitoring of a disease progression, such as rheumatoid arthritis, or comparison between patients. |
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H71.00115: Performance and Robustness of Machine Learning-based Radiomic COVID-19 Severity Prediction Zan Klanecek, Shotaro Naganawa, John Kim, Luciano Rivetti, Andrej Studen, Stephen S.F. Yip, Robert Jeraj Manual assessment of CTs has shown great promise in determining COVID-19 (C19) severity, however it is laborious and subtle CT findings can be overlooked. To address these problems, we developed and analyzed the performance and robustness of a logistic-regression (LR) model in predicting C19 severity in a large public cohort of 1110 patients. |
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H71.00116: Analytical treatment of radiative transfer equation for analysis of medical hyperspectral images Matija Milanic, Jost Stergar, Martin Horvat Transport of light in biological tissues is commonly modelled by solving radiative transfer equation (RTE). In the past only indirect or approximate solutions of RTE were used. Recently, analytical solutions of RTE for specific geometries emerged, yet without a thorough evaluation of convergence and accuracy. |
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H71.00117: Liver Cancer Risk Quantification through Artificial Neural Network Afrouz Ataei, Touhid Feghhi, Theodora Leventouri, Dr. Wazir Muhammad Liver cancer is the sixth most common type of cancer worldwide and is the third leading cause of cancer related mortality. Several types of cancer can form in the liver. The most common type of liver cancer is hepatocellular carcinoma (HCC). While the exact cause of liver cancer may not be known, habits/lifestyle may increase the risk of developing the disease. Several risk prediction models for HCC are available for individuals with hepatitis B and C virus infections who are at high risk but not for general population or unknown risk. Artificial neural networks (ANN) are the mathematical algorithm, generated by computers and are widely used in the field of medicine due to its potential for diagnostic and prognostic applications. In this study an ANN model was developed, trained, and tested using the health data captured from the National Health Interview Survey to predict liver cancer risk. Results indicate that our ANN can be used to predict liver cancer risk with changes with life style and may provide a novel approach to identify patients at higher risk and can be benefited from early diagnosis. |
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H71.00118: Application of deep learning for efficacy of radiation treatment for lung cancer Touhid Feghhi, Shahabeddin Mostafanazhad aslmarand, Afrouz Ataei, Dr. Wazir Muhammad Lung cancer is one of the most fatal cancers in the United States. The type of treatment heavily depends on the stage and histology of lung cancer. Often, we need to use radiotherapy in conjunction with chemotherapy and surgery to treat patients with lung cancer. The aim is to kill the cancer cells while minimizing radiation to healthy tissue and important organs in the vicinity of treatment area. Although modern radiation oncology has a proven and predicable role for lung cancer treatment with gains in quality, efficacy, toxicity, and outcomes, still we have local treatment failure. Also, the damage to the normal tissue around the tumor (fibrous) can lead to severe post treatment issues/toxicities for the patients. Therefore, the goal of this project is to quantify the effect of radiation in eliminating the tumor and predicting post-treatment toxicities/complications. For this purpose, we develop a convolutional neural network algorithm for tracking the efficacy of treatment. We will use pre- and post-treatment CT scan and PET images, with blood test results and radiation dose data of the patients. In such way we will predict outcomes of the treatment in terms of dose coverage to the tumor target and OARs per Quantitative Analysis of Normal Tissue Effects in the Clinic. |
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H71.00119: Investigation antiviral effects of cold atmospheric plasma Milad Rasouli, Elaheh Amini Gas plasma has wide applications in medical science such as cancer treatment, virus inactivation, and wound healing. A typical plasma plume is generated by feeding a noble gas through a pair of electrodes with a couple of kV sinusoidal waves. Cold atmospheric plasma as a cocktail of physical and chemical factors provides a solution for the drawbacks of common antiviral methods. Gas plasma technology provides a perspective for the general audience of the chances and opportunities for supporting healthcare during viral pandemics such as the COVID-19 crisis. Plasma with complex constituents such as the emission of UV radiation and reactive oxygen and/or nitrogen species (RONS) have the most important antimicrobial properties and is a novel, efficient, and clean solution for virus inactivation. Here, we aim to investigate virus inactivation efficiency of cold plasma on SARS-CoV-2 model viruses. Besides, we measure the concentration of long-lived reactive oxygen and nitrogen species (RONS) to elucidate the chemical effects of cold plasma. We will perform Ethidium monoazide (EMA)-coupled RT-qPCR for investigating the inactivation performance of non-thermal plasma. |
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H71.00120: Auto segmentation, detection, and countering of Lung nodule using convolutional neural networks Shahabeddin Mostafanazhad aslmarand, Touhid Feghhi, Dr. Wazir Muhammad
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H71.00121: Rapid Calcuation of Scatter Corrections in Medical X-Ray Computed Tomography Zachary Levine With a small approximation, it is possible to transfer the effect of the inelastic scattering atomic form factor to the eleastic scattering atomic form factor because there is little energy loss in small angle scattering. The adjusted inelastic scattering is much smoother than the original. Hence, it can be sampled using fixed, forced detection on an extremely small grid. The adjusted elastic scattering is handled efficiently with conventional Monte Carlo. Multiple scattering of mixed type is treated as inelastic scattering. Estimates of the improvement in computational times are given compared to a conventional fixed, forced detection approach. |
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H71.00122: Characterization of proton pencil beam dosimetry and optics of the first 360 degree rotational single room ProBeam Compact™ (Varian Medical) Shreen Fathallah Among all types of radiotherapy, proton therapy has a great potential to deliver a high dose to the tumor volume with a minimum of dose to the surrounding tissues. Knowledge of therapeutic proton beam characteristics is therefore essential for its successful management in cancer treatment. The purpose of our work is to characterize the dosimetry and optics for the scanning pencil proton beam of the first 360 degree rotational Varian™ ProBeam compact machine at South Florida Proton Therapy Institute. The measurements used for the commissioning of the provided Treatment Planning System (TPS) and include integrated depth doses (IDDs), absolute dose measurements, and in air spot profiles. The widths of Bragg peaks (Rb80 -Ra80) of IDDs were from 2.33 mm for 70 MeV to 9.70 mm for 220 MeV within the specifications. The surface beam Spot profiles were fitted by single Gaussian distributions using in-house Python code. The average beam spot sigma ranged from 5.89 mm to 3.32 mm for 70 MeV to 220 MeV. Characterization of the pencil scanning proton beam dosimetry and optics are presented in this investigation for Varian first ProBeam Compact™ scanning proton therapy machine. |
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H71.00123: Development of an Innovative Daily QA System for Pencil-Beam Scanning Proton Therapy Maxwell Kassel The goal of this study is to create a simplified procedure for a scanning proton therapy machine daily QA according the requirements specified by American Association of Physics in Medicine Task Group Report 224 (TG 224). A novel phantom and methodology was created for the daily QA process consisting of (1) multiple rectangular homogeneous acrylic block columns; (2) an innovative multi-PTV proton plan; and (3) SunNuclear Daily QA3 multi-chamber detector array. The procedure validated the accuracy of proton beam output, energy/range, and pencil-beam spot positions. The QA tolerance levels outlined by the American Association of Physics in Medicine Task Group Report 224 (TG 224) can also be applied during analysis which can be triggered for pass/fail. By using this innovative Daily QA method, all essential dosimetric checks recommended by TG 224 were achieved with a simple setup and a single beam delivery. During initial tests and clinical practice, this innovative daily QA program has verified output, energy, and spot positions with high reproducibility and accuracy in a time efficient manner. |
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H71.00124: Characterization of proton pencil beam dosimetry and optics of the first 360 degree rotational single room ProBeam Compact™ (Varian Medical) Shreen Fathallah, Dr. Charles Shang, Theodora Leventouri, Dr. Wazir Muhammad Among all types of radiotherapy, proton therapy has a great potential to deliver a high dose to the tumor volume with a minimum of dose to the surrounding tissues. Knowledge of therapeutic proton beam characteristics is therefore essential for its successful management in cancer treatment. The purpose of our work is to characterize the dosimetry and optics for the scanning pencil proton beam of the first 360 degree rotational Varian™ ProBeam compact machine at South Florida Proton Therapy Institute. The characterizations used for the commissioning of the provided Treatment Planning System (TPS) and include integrated depth doses (IDDs), absolute dose measurements, and in air spot profiles. The widths of Bragg peaks (Rb80 -Ra80) of IDDs were from 2.33 mm for 70 MeV to 9.70 mm for 220 MeV within the specifications. The surface beam Spot profiles were fitted by single Gaussian distributions using in-house Python code. The average beam spot sigma ranged from 5.89 mm to 3.32 mm for 70 MeV to 220 MeV. Characterization of the pencil scanning proton beam dosimetry and optics are presented in this investigation for Varian first ProBeam Compact™ scanning proton therapy machine. |
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H71.00125: QUANTUM INFORMATION
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H71.00126: QGameTheory: A Quantum Game Theory Simulator written in R for teaching quantum computing and game theory to starting programmers and undergraduate students Indranil Ghosh Quantum game theory has become an enlivening field of study that makes use of quantum manipulations to model the interplay between participating agents/players. These players, as a result, apply quantum strategies instead of the classical versions, as studied in classical game theory. |
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H71.00127: Quantum Otto Engine with Interacting Particles Jacob McCready, Nathan M Myers, Sebastian Deffner The performance and operation of quantum heat engines differ from their classical analogues due to the unique effects that result from quantum mechanical phenomena. Hence, the study of these quantum phenomena and their impact on engine performance is important to the understanding of the thermodynamics of the quantum realm. The exchange statistics of indistinguishable particles is one such uniquely quantum property that can be exploited to enhance the thermodynamic efficiency and power output of a quantum heat engine. To this end, we examine a quantum Otto engine with a harmonic working medium that consists of two contact-interacting particles, either bosons or fermions. For scale-invariant driving, we explore the interplay between inter-particle interactions and wave function symmetry features on engine performance. |
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H71.00128: In A Null Measurement, Where Is The Uncertainty Principle? Nowhere To Be Found-
The Uncertainty Principle Does Not Protect A Null Measurement: Knowledge Does Douglas Snyder
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H71.00129: The Change in Probability Distributions for the 2-Slit Experiment from Interference to Knowing the Specific Way an Event Occurred is Protected by Knowledge, Not the Uncertainty Principle Douglas Snyder A prior analysis of an adaptation of Einstein’s 2-slit experiment with momentum control through the use of putting the slit plate on wheels is discussed. This analysis, congruent with the explanation by Bohr, relies on the uncertainty principle to explain the presence of no interference in the probability distribution instead of interference. The correct explanation is based on the principle that when one can know the specific way an event takes place, one takes the absolute square of the probability amplitude for the event for a specific way to develop the probability distribution for the event happening that specific way. The total probability distribution is the sum of the probability distributions for the event happening either of the two possible ways (no interference). Bohr used the uncertainty principle “to escape the paradoxical necessity of concluding that the behaviour of an electron or a photon should depend on the presence of a slit in the diaphragm through which it could be proved not to pass.” Bohr preferred phase incongruence for the components of the wave function through the 2 slits even though 1 component, including its phase, vanishes as soon as the specific way the event occurred is known. The new explanation explains null measurements. Bohr’s does not. |
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H71.00130: Optimal state estimaion in Arthurs-Kelly scheme with modified Hamiltonian Chandan Kumar, Arvind Arvind Arthurs and Kelly considered the joint measurement of conjugate observables, which eventually resolved the dilemma surrounding various uncertainty principles. They extended the von Neumann model, where the system was coupled with two detectors using an interaction Hamiltonian. In this work, we further advance the research by modifying the interaction Hamiltonian, leading to correlated detectors [1]. Our analysis shows that the optimal state estimation corresponds to uncorrelated detectors. These results enhance our understanding of the uncertainties associated with joint measurements of conjugate observables in a general situation and will be of direct relevance in various quantum protocols in the area of continuous-variable quantum information processing. Phase space techniques and the application of the real symplectic group Sp(6, R) significantly simplify the analysis [2]. |
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H71.00131: Distinguishability as a Resource – Thermodynamic Characterization of 1D Anyons Nathan Myers, Sebastian Deffner In low-dimensional systems, indistinguishable particles can display statistics that interpolate between those of bosons and fermions. Signatures of these “anyons” have been detected in two-dimensional quasiparticle excitations of the fractional quantum Hall effect, however experimental access to these quasiparticles remains limited. In one dimension, anyonic behavior can be realized through a statistical mixture of entangled particles. Here we develop the full thermodynamic characterizations of one-dimensional anyons, including both equilibrium and nonequilibrium behavior. The performance of a quantum heat engine with an anyonic working medium is explored, demonstrating a rich dependence on the anyonic phase. In addition, methods of optimizing engine performance through shortcuts to adiabaticity are investigated, using both linear response and fast forward techniques. |
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H71.00132: Character randomized benchmarking for non-multiplicity-free groups with applications to subspace, leakage, and matchgate randomized benchmarking Jahan Claes, Eleanor G Rieffel, Zhihui Wang Randomized benchmarking (RB) is a powerful method for determining the error rate of quantum gates. However, classical RB is restricted to gatesets like the Clifford group that form a unitary 2-design. The recently introduced character RB can benchmark more general gates using techniques from representation theory; however, this method has only been explored for “multiplicity-free” groups, limiting its applicability. In this talk, I’ll present a generalization of character RB that explicitly includes non-multiplicity-free groups, and three example applications. First, I’ll give a rigorous version of the recently introduced subspace RB[1] for characterizing the Honeywell entangling gate. Second, I present a leakage RB that applies to more general gates than the original[2]. Finally, I’ll demonstrate a scalable RB protocol for the matchgate group. This represents one of the few examples of a scalable non-Clifford RB. I’ll also discuss the potential of using character RB to characterize specific gates and find new examples of scalable RB. |
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H71.00133: Modeling the Antenna Mode of the Transmon Qubit Owen Rafferty, Sohair Abdullah, Chris Wilen, Robert F McDermott We describe analytical and numerical studies of the spurious antenna mode of the transmon qubit. Through coupling to this mode, the qubit can become an efficient absorber of pair-breaking radiation. We describe a scheme to exploit this antenna coupling for the purposes of dark matter detection. Here, photons transduced from dark matter axions are converted to quasiparticles in a weakly charge-sensitive qubit. Ramsey-based charge tomography provides access to the quasiparticle parity of the qubit island. This approach provides access to the axion mass range from 10 GHz to 10 THz, a region of phase space that is difficult to access using existing methods. |
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H71.00134: A time-symmetric formulation of quantum entanglement resolves paradoxical aspects of the conventional formulation Michael Heaney I numerically simulate and compare the entanglement of two quanta using the conventional formulation of quantum mechanics and a time-symmetric formulation that has no collapse postulate. The experimental predictions of the two formulations are identical, but the entanglement predictions are significantly different. The time-symmetric formulation reveals an experimentally testable discrepancy in the original quantum analysis of the Hanbury Brown-Twiss experiment, suggests solutions to some parts of the nonlocality and measurement problems, fixes known time asymmetries in the conventional formulation, and answers Bell's question "How do you convert an 'and' into an 'or'?" |
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H71.00135: A tentative plasma-like interpretation of elementary and composite particles in quantum theory Andrey Akhmeteli Schrödinger noticed in 1952 that a scalar complex wave function can be made real by a gauge transformation. It was shown recently that one real function is also enough to describe matter in more realistic theories, such as the Dirac equation in an arbitrary electromagnetic or Yang-Mills field. As these results suggest some "symmetry" between positive and negative frequencies and, therefore, particles and antiparticles, the author previously considered an interpretation of one-particle wave functions as plasma-like collections of a large number of particles and antiparticles. This work offers a criterion for approximation of continuous charge density distributions by discrete ones with quantized charge based on the equality of partial Fourier sums. An example of such approximation is computed using the homotopy continuation method. An example mathematical model of the interpretation is proposed. A modification of the interpretation for composite particles, such as nucleons or large molecules, describes them as collections including a composite particle and a large number of pairs of elementary particles and antiparticles. While it is not clear if such an interpretation describes the reality correctly, it can become a basis of an interesting model of quantum mechanics. |
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H71.00136: 648 Hilbert-space dimensionality in a biphoton frequency comb Kai-Chi chang, Xiang Cheng, Murat Can Sarihan, Abhinav Kumar Vinod, Yoo Seung Lee, Tian Zhong, Yan-Xiao Gong, Zhenda Xie, Jeffrey H Shapiro, Franco Wong, Chee Wei Wong Qudit entanglement is a valuable resource for quantum information processing because increasing dimensionality provides a pathway to higher capacity and increased error resilience in quantum communications, cluster-state quantum computation, and quantum phase measurements. Time-frequency entanglement enables qudit encoding equivalent to multiple qubits per particle that is bounded only by the spectral correlation bandwidth and readout timing jitter. Our interest is in the discrete-variable time-frequency entanglement afforded by filtering the signal and idler outputs from a continuous-wave-pumped spontaneous parametric downconverter (SPDC) to create a biphoton frequency comb (BFC). Using a fiber Fabry- Pérot cavity with 45.32 GHz free-spectral range and 1.56 GHz full-width-at-half-maximum (FWHM) linewidth to filter the outputs from a type-II quasi-phase-matched SPDC source, we generate a BFC whose time-binned Hilbert space dimensionality is at least 324. When combined with its post-selected polarization entanglement, this BFC's dimensionality doubles to at least 648, implying it has a 6.28 bits/photon classical-information capacity. |
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H71.00137: Error Suppression in Continuous-time Quantum Computing Jemma Bennett, Tom O'Leary, Mia West, Nicholas Chancellor, Viv Kendon Compared to the circuit model of quantum computation, there has been more limited work on Hamiltonian error suppression (HES), described in [Crosson, & Lidar, arXiv:2008:09913v1, 2020]. Building on an idea proposed in [Young et al., Phys. Rev. A88, 062314, 2013], multiple copies k of a small Ising spin model can be linked together via ferromagnetic or anti-ferromagnetic links. This increases the logical system's robustness to error. Numerical methods show that copies connected via anti-ferromagnetic links perform better than those connected via ferromagnetic links in some cases. A protocol enables us to determine for which models anti-ferromagnetic links are beneficial, allowing us to harness this performance improvement. This technique shows promise for increasing the robustness and precision in continuous-time quantum computing. |
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H71.00138: Faster Digital Quantum Simulation by Symmetry Protection Minh Tran, Yuan Su, Daniel Carney, Jacob Taylor Simulating the dynamics of quantum systems is an important application of quantum computers. We show that by introducing quantum gates implementing unitaries generated by the symmetries of the system, one can induce destructive interference between the errors from different steps of the simulation, effectively giving faster simulation by symmetry protection. We derive rigorous bounds on the error of a symmetry-protected simulation and identify conditions for optimal protection. In particular, when the symmetry transformations are chosen as powers of a unitary, the simulation error is approximately projected to the so-called quantum Zeno subspaces. We prove a bound on this approximation error, exponentially improving a recent result of Burgarth, Facchi, Gramegna, and Pascazio. We apply the technique to the simulations of the XXZ Heisenberg interactions with local disorder and the Schwinger model in quantum field theory. For both systems, the technique can reduce the simulation error by several orders of magnitude over the unprotected simulation. Finally, we provide numerical evidence suggesting that the technique can also protect simulation against other types of coherent, temporally correlated errors, such as the $1/f$ noise commonly found in solid-state experiments. |
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H71.00139: Self-guided method to search for EPR state correlations using uncalibrated polarization controllers in a plug-and-play optical system. Evan Dowling, Rajarshi Roy, Thomas Murphy Observing nonlocal correlations between entangled photons is a staple of many quantum information tasks. The measurement bases between two observers recording nonlocal correlations are often oriented with free space optical waveplates. Instead, we use uncalibrated piezoelectric actuator polarization controllers to align our observers’ measurement bases where the alignment is done through photon counting feedback and a stochastic gradient descent algorithm. This plug-and-play, fully fiber optic system eliminates many experimental complexities such as free-space optical component alignments and free-space-to-fiber couplings. We experimentally study the speed and stability of this alignment on a two-qubit entangled photon source with noise. We postulate on this method's ability to be used on future feedback Bell inequality experiments and the calibration of uncalibrated polarization controllers[1]. This simplified experimental setup may be of use for automated alignment of future quantum information systems. |
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H71.00140: Quantifying the Performance of Bidirectional Quantum Teleportation Aliza Siddiqui, Mark Wilde Bidirectional teleportation is a fundamental protocol for exchanging quantum |
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H71.00141: The controlled SWAP test for determining quantum entanglement Steph Foulds, Viv Kendon, Tim Spiller Quantum entanglement is essential to the development of quantum computation, communications, and technology. The controlled SWAP test, widely used for state comparison, can be adapted to an efficient and general test for entanglement. We build on the work of van Dam et al. in their 2008 patent which shows that the 2-qubit c-SWAP test evidences entanglement and details an optical implementation; and Gutoski et al. [Theory Comput. 11: 59, 2015] which proves the product-state c-SWAP test is a complete problem for BQP. Here we show that for any n-qubit pure state, the test can evidence the presence of entanglement (and further, genuine n-qubit entanglement), can distinguish entanglement classes, and generates the concurrence in the case of a 2-qubit state. We also propose a multipartite degree of entanglement, related to the test's probability outputs. The average number of measurements required to detect entanglement increases with decreased entanglement. Maximally entangled states require fewer measurements the larger the system, two on average for many (n≥8) qubits. Furthermore, the results are robust to second order when typical small errors are introduced to the state under investigation. Details in arXiv:2009.07613 |
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H71.00142: Hybrid III-V diamond photonic platform for quantum nodes based on neutral silicon vacancy centers in diamond Alexander Abulnaga, Ding Huang, Sacha Welinski, Mouktik Raha, Zihuai Zhang, Paul Stevenson, Jeff Thompson, Nathalie De Leon Integrating quantum memories based on color centers in diamond with on-chip photonic devices may enable entanglement distribution over long distances, but efforts towards integration have been challenging as color centers are sensitive to their environment and their properties degrade in nanofabricated structures[1]. We present a heterogeneously integrated, on-chip, III-V diamond platform designed for neutral silicon vacancy (SiV0) centers. The combination of stable optical transitions and long spin coherence times makes the SiV0 center an attractive candidate for nodes in quantum networks[2,3]. Our design does not require etching the diamond substrate, thus avoiding material damage and spectral diffusion arising from nanofabrication. Through evanescent coupling to SiV0 centers near the diamond surface, the platform can enable Purcell enhancement of SiV0 emission and quantum frequency conversion to the telecommunication C-band. |
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H71.00143: Verification of Diagnostic Circuits on IBM Quantum Circuits: Using Hybrid Machine Learning for Fault Classification Roy Pace, Margarite L LaBorde, Aliza Siddiqui, Britta Manifold Previous projects proposed an fault identification scheme to isolate faulty quantum logic gates, using hybrid machine learning. This procedure was implemented onto real IBM quantum computers through the IBM Quantum Experience, cloud based open access network of quantum computers. We demonstrate that through the use of neural networks, the project was actualized. The presentation will focus on the creation and implementation of an appropriate neural network, capable of properly identifying gate faults on circuits of multiple gates and varying types. |
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H71.00144: Depth optimization of quantum search algorithms beyond Grover's algorithm Kun Zhang, Vladimir Korepin Grover's quantum search algorithm provides a quadratic speedup over the classical one. The computational complexity is based on the number of queries to the oracle. However, depth is a more modern metric for noisy intermediate-scale quantum computers. We propose a new depth optimization method for quantum search algorithms. We show that Grover's algorithm is not optimal in depth. We propose a quantum search algorithm, which can be divided into several stages. Each stage has a new initialization, which is a rescaling of the database. This decreases errors. The multistage design is natural for parallel running of the quantum search algorithm. |
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H71.00145: What is the physical meaning of the quantum wave function? Donald Chang About a hundred years ago, there was a famous debate between Bohr and Einstein: Does the quantum wave function of an electron have a physical meaning beyond probability? This question is still open today. This work proposes a new theoretical framework to address the above question. Our approach is that, based on observations that photons and electrons have similar wave properties, we hypothesize that both of them are quantized excitation waves of the vacuum, the physical properties of which can be modelled based on the Maxwell theory. Using the method of Helmholtz decomposition, we showed that the wave function of the particle is associated with an electric vector potential called “Z”, which plays the role of basic field for the excitation wave. Using this framework, the quantum wave equations of electron can be derived directly from the Maxwell theory. |
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H71.00146: Time-Resolved Quantum Process Tomography of a Compact 3D Quantum Memory Yuki Nojiri, Frank Deppe, Michael Renger, Qiming Chen, Stefan Pogorzalek, Matti Partanen, Kirill Fedorov, Achim Marx, Rudolf Gross Storing a photonic state in a 3D superconducting cavity as long as possible and reading out its information as fast as possible is a challenging task due to the conflicting requirements regarding the coupling strength between the cavity and readout circuit. This problem can be solved by a multimode compact 3D memory scheme employing a wealky and strongly coupled storage and readout mode with both coupled to a transmon qubit [Xie et al., Appl. Phys. Lett. 112, 202601 (2018)]. However, comparing the experimental data of the time evolution of the quantum process tomography with an empirical simulation, we saw difference in the relaxation behavior become obvious. To clarify this issue we perform an ab initio quantum simulations. In particular, these simulations allow us to understand yet unknown physics behind the compact 3D memory design and improve the protocol for the quantum memory process. |
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H71.00147: Coherence protection and decay mechanism in qubit ensembles under concatenated continuous driving GUOQING WANG, Yi-Xiang Liu, Paola Cappellaro Dense ensembles of spin qubits are valuable for quantum applications, even though their coherence protection remains challenging. Continuous dynamical decoupling can protect ensemble qubits from noise while allowing gate operations, but it is hindered by the additional noise introduced by the driving. Concatenated continuous driving (CCD) techniques can, in principle, mitigate this problem. We experimentally demonstrate the improved control by simultaneously addressing a dense Nitrogen-vacancy (NV) ensemble with 10^10 spins. We achieve an experimental 15-fold improvement in coherence time for an arbitrary, unknown state, and a 500-fold improvement for an arbitrary, known state, corresponding to driving the sidebands and the center band of the resulting Mollow triplet, respectively. By extending the generalized Bloch equation approach to the CCD scenario, we identify the noise sources that dominate the decay mechanisms in NV ensembles, confirm our model by experimental results, and identify the driving strengths yielding optimal coherence. Our results can be directly used to optimize qubit coherence protection under continuous driving and bath driving, and enable applications in robust pulse design and quantum sensing. |
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H71.00148: Phase Transition Dynamics of Quantum Information Zhi an Luan In the CAP 2019 Congress, my 3 papers cast the Generalized Newton’s Laws (GNL)by the form: GMV=Id in torus S1, and an Spectrum Triple (G,h, kB ) as a main scheme. |
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H71.00149: The Nakano-Nishijima-Gell-Mann Formula From Discrete Galois Field Satoshi Tanda, Keiji Nakatsugawa, Motoo Ohaga, Toshiyuki Fujii, Toyoki Matsuyama If the world has a finite compact space (I120: Poincare Dodecahedron) [1] and discrete coordinates [2,3], what happens? In this case, the problem of infinities in gravity and in the standard model might be avoided. To avoid this problem, quantum gravity theories such as the superstring theory or the loop quantum gravity are developing, but neither of those theories have been completed. We reconstruct the Nakano-Nishijima-Gell-Mann (NNG) formula by using a discrete Galois field without using continuous coordinate. When we reconstruct new theories with a Galois field, these new theories must satisfy fundamental conservation law related to unitary, Lorentz, and gauge invariance. |
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H71.00150: Mitigating errors in noisy quantum computers Samuele Ferracin, Nate T. Stemen, Joel Wallman The effectiveness of Quantum Error Mitigation (QEM) protocols depends crucially upon the capability of reconstructing noise processes in experimental setups. In the available QEM protocols, this reconstruction is performed by analyzing individual gates acting on one or two qubits and does not account for noise processes that correlate many qubits, such as cross-talks. To overcome this limitation, we provide a set of QEM protocols that rely on noise reconstruction techniques designed to efficiently reconstruct noise processes affecting a large number of qubits, potentially the whole register. Exploring different approaches, we enhance existing methods (such as quasi-probabilistic error cancellation) and propose novel techniques (which we call “cycle extrapolation” and “circuit repetition”) to drastically upgrade the performance of noisy quantum computers. Making only mild assumptions on the hardware, we rigorously quantify the effectiveness and overhead of all our protocols. Overall, our work offers the tools to significantly improve the outputs of noisy quantum computers, as well as to build confidence in these outputs by reproducing them with different techniques. |
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H71.00151: A quantum encryption scheme featuring confusion, diffusion, and mode of operation Zixuan Hu, Sabre Kais Quantum cryptography – the application of quantum computing techniques to cryptography has been extensively investigated. Two major directions of quantum cryptography are quantum key distribution (QKD) and quantum encryption, with the former focusing on secure key distribution and the latter focusing on encryption using quantum algorithms. In contrast to the success of the QKD, the development of quantum encryption algorithms is limited to designs of mostly one-time pads (OTP) that are unsuitable for most communication needs. In this work we propose a non-OTP quantum encryption scheme utilizing a quantum state creation process to encrypt messages. As essentially a non-OTP quantum block cipher the method stands out against existing methods with the following features: 1. complex key-ciphertext relation (i.e. confusion) and complex plaintext-ciphertext relation (i.e. diffusion); 2. mode of operation design for practical encryption on multiple blocks. These features provide key reusability and protection against eavesdropping and standard cryptanalytic attacks. |
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H71.00152: Simulations of Magnetic Noise in Classical XY and Heisenberg Spin Models Dan Mickelsen, Herve M. Carruzzo, Ruqian Wu, Clare Yu Superconducting qubits show great promise but continue to be plagued by flux noise. Experiments show that surface spins are the source of this flux noise, and the noise has a power spectral density of the form 1/fα with the noise exponent α~1. We present the results of Monte Carlo simulations of the magnetic noise produced by coupled classical XY and Heisenberg spins in 2D lattices. |
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H71.00153: Quantum random access memory via quantum walk Ryo Asaka, Kazumitsu Sakai, Ryoko Yahagi A novel concept of quantum random access memory (qRAM) employing a quantum walk is provided. Our qRAM relies on a bucket brigade scheme to access the memory cells. Introducing a bucket with chirality left and right as a quantum walker, and considering its quantum motion on a full binary tree, we can efficiently deliver the bucket to the designated memory cells, and fill the bucket with the desired information in the form of quantum superposition states. Our procedure has several advantages. First, since the bucket is free from any entanglement with the quantum devices at the nodes on the binary tree, our qRAM architecture may be more robust against quantum decoherence. Second, our scheme is fully parallelized. Consequently, only O(n) steps are required to access and retrieve O(2^n) data in the form of quantum superposition states. Finally, the simplicity of our procedure may allow the design of qRAM with simpler structures. |
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H71.00154: The literature of new physics Philip Shin We can write literature as grammar letter written for composition that can be physics formula. There are a lot of possibility to create new letter by literature that is almost poem. The story becomes grammar to make new physics theory by the best plot of literature. Greater composition becomes the better physics theory. |
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H71.00155: Integration of 4-8GHz Cryogenic Low Noise Mixer Using AC Josephson effect in Quantum Computation System Hyeok Hwang, JeaKyung Choi, Eunseong Kim For RF signal processing, frequency conversion using diode mixer is one of the most essential techniques. In the case of various cryogenic RF systems (such as quantum computation system, MEMS, etc.), the thermal noise of the system is extremely low. The diode mixer based on Schottky effect has lower knee-voltage compared to other mixer, but it has a much higher voltage scale (~300mV) compared to the signals of the cryogenic RF system (~100nV). Therefore, despite the high purity of such RF systems, we usually mix signals in high temperature environments. Since the proposal for Josephson mixer in 1972, the method of using Josephson relation in superconductors has been extensively studied in mm-wavelength system of radio astronomy. We would like to apply the concept of Josephson mixer to our 4-8GHz single-photon-limit cryogenic system. First, we verified the manufacturability of Josephson mixer, which operates in our RF cryogenic system. Applying the Bessel-Fourier series expansion to the situation of mixing two RF signals, the amplitude of each mixed frequency components is reproduced as Bessel function of the first kind, and we could obtain realistic conditions of junction size and mixing signals. It is followed by the fabrication of Josephson mixer with suitable notch filters. |
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H71.00156: Loss mechanism in Silicon in the quantum regime Mattia Checchin, Anna Grassellino, Alexander Romanenko In this study we present a detailed study of the loss mechanism of Silicon in the quantum regime. We measure the loss tanget for several types of Silicon substrates as a function of temperature, frequency and photon number. |
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H71.00157: QAOA Applications in Finance Nathan White, Kaiwen Gui, zain Saleem, Martin Suchara The Quantum Approximate Optimization Algorithm (QAOA) is a hybrid quantum algorithm designed to meet the constraints of Noisy Intermediate Scale Quantum (NISQ) computers. QAOA has been used to approximate NP-hard optimization problems. In this work we apply QAOA to study portfolio optimization problems that minimize portfolio volatility and maximize return. We design and examine different types of QAOA algorithms, evaluate their performance using the IBM Qiskit simulator, and benchmark the performance against the corresponding classical approximation and exact algorithms. In numerical experiments, we find our approach in some cases outperforms existing methods. Specifically, we present a novel technique that uses both pre-processing and post-processing of the trial solutions obtained from QAOA. The objective functions we encode on the cost Hamiltonian are either partial objectives, or some replacements of the classically non-convex problems. |
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H71.00158: Classical Circuit Simulations for Superconducting Quantum Circuits Alan Kadin Qubits based on superconducting circuits are being actively developed for quantum computing. Superconducting circuits with the same elements are also used for classical electronic circuits, and are simulated using standard classical circuit simulation tools. The theory of quantum circuits requires fundamental uncertainty, superposition, and entanglement, which are not included in classical models. For this reason, few quantum experiments make comparisons to classical simulations. However, some researchers have shown that classical simulations of superconducting circuits can account for observations on Josephson junctions that have otherwise been attributed to uniquely quantum effects [1]. This analysis is extended here to coupled superconducting oscillators, which are similar to quantum circuits explored in experiments. Classical circuit simulations of complex superconducting circuits can be readily carried out, and can be compared to measurements of coupled superconducting qubits. In this way, it may be possible to more clearly distinguish true quantum effects from those which may have a classical explanation. |
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H71.00159: Some Remarks on the Entanglement Number George Androulakis, Ryan McGaha Gudder, in a recent paper, defined a candidate entanglement measure which is called the entanglement number. The entanglement number is first defined on pure states and then it extends to mixed states by the convex roof construction. In Gudder's article it was left as an open problem to show that Optimal Pure State Ensembles (OPSE) exist for the convex roof extension of the entanglement number from pure to mixed states. We answer Gudder's question in the affirmative, and therefore we obtain that the entanglement number vanishes only on the separable states. More generally we show that OPSE exist for the convex roof extension of any function that is continuous on the pure states of a finite dimensional Hilbert space. Further we prove that the entanglement number is an LOCC monotone,(and thus an entanglement measure), by using a criterion that was developed by Vidal in 2000. For self-containment, we reproduce Vidal's proof by presenting an interesting point of view of tree representations for LOCC communications. Lastly, we generalize Gudder's entanglement number by producing a monotonic family of entanglement measures that relates to the entanglement of formation in a natural way. |
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H71.00160: Exploring the effect of noise on (polyfractal) driving to create multiple symmetries in many-body quantum systems Tristan Martin, Kartiek Agarwal, Ivar Martin Symmetries (and their spontaneous rupturing) can be used to protect and engender novel quantum phases and lead to interesting collective phenomena. In [1], the authors described a general dynamical decoupling (“polyfractal”) protocol that can be used to dynamically engineer multiple discrete symmetries in many-body systems. The present work expands on [1] by studying the effect of noise on such a dynamical scheme. To make the analysis tractable, and numerical simulations efficient, we insert errors in the pattern of a Fibonacci replacement sequence. We find generically that the scheme yields symmetries that are protected up to exponentially long times in the inverse error rate. We also discuss how such symmetries can be engineered to protect quantum information and the affect of noise using this scheme. |
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H71.00161: Quantum computed moments correction to variational estimates Harish Vallury, Charles Hill, Lloyd C. L. Hollenberg The variational principle of quantum mechanics is an important hybrid quantum algorithm in many applications. However, as the problem size grows, so does the trial-state circuit and quantum logic errors can easily overwhelm the quality of the results. Here we present an approach (arxiv.org/abs/2009.13140) based on quantum computed Hamiltonian moments <H^n>, which provide a correction to the variational result <H> for the ground-state energy of a given problem. Estimates of the ground-state energy are obtained from the computed moments using the infinum theorem from Lanczos cumulant expansions. The method is introduced and demonstrated on 2D quantum magnetism models on lattices up to 5x5 (25 qubits) implemented on IBM Quantum superconducting qubit devices. Moments were computed to fourth order with respect to an antiferromagnetic trial-state. A comparison with benchmark variational calculations showed that the infinum estimate not only consistently outperformed the benchmark variational approach for the same trial-state, but also displayed a high degree of stability against trial-state variation, quantum gate errors and shot noise for this problem. |
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H71.00162: Dynamic Quantum Variational Ansatz Bilal Tariq, zain Saleem, Martin Suchara Quantum Approximate Optimization Algorithm is a variational algorithm that uses both classical and quantum resources to find the approximate solution to combinatorial optimization problems. The algorithm attempts to find the best solution by classically optimizing the expectation value of the objective function in the variational ansatz. We discuss a new algorithm based on a "Dynamic Quantum Variational Ansatz" (DQVA) for the maximum independent set problem that dynamically reduces the depth of the circuit used in preparing the variational ansatz employed in the quantum optimization [1]. The algorithm can be also applied to other constrained combinatorial optimization problems. |
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H71.00163: Matchgate benchmarking: Scalable benchmarking of a continuous family of many-qubit gates Jonas Helsen, Sepehr Nezami, Matt Reagor, Michael Walter We propose a method to reliably and efficiently extract the fidelity of many-qubit quantum circuits composed continuously parametrized two-qubit gates. |
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H71.00164: Witnesses of coherence and dimension from multiphoton indistinguishability tests Taira Giordani, Chiara Esposito, Francesco Hoch, Gonzalo Carvacho, Daniel Brod, Ernesto Galvão, Nicolò Spagnolo, Fabio Sciarrino Quantum coherence is a resource with a lot of application in quantum computing and quantum information, and more in general is studied in the foundations of quantum mechanics. It is of interest to find protocols to verify its presence that are simple and reliable. Currently there exist some methods of coherence witness that are based on a family of observables whose result can check if a state is not diagonal in a given base. Here we experimentally test a novel type of coherence witness based on state comparison to detect sperpositions in a basis-independent way. Our experiment uses a linear interferometer to perform three Hong-Ou-Mandel tests simultaneously to measure pairwise overlaps between three single-photon states. |
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H71.00165: An optimal quantum sampling regression algorithm for variational eigensolving in the low qubit number regime Pedro Rivero, Ian Cloet, Zack E Sullivan The VQE algorithm, with all its merits, has turned out to be quite expensive to run given the way we currently access quantum processors (i.e. over the cloud). In order to alleviate this issue, in this paper we introduce an alternative hybrid quantum-classical algorithm, and analyze some of its use cases based on time complexity in the low qubit number regime. In exchange for some extra classical resources, this novel strategy is proved to be optimal in terms of the number of samples it requires from the quantum processor. We develop a simple —yet general— analytical model to evaluate when this algorithm is more efficient than VQE, and, from the same theoretical considerations, establish a threshold above which quantum advantage can occur. Finally, we then make use of this novel method to simulate a simplified model of NJL: an effective quantum field theory based on the BCS theory of superconductivity. Our goal with this work is to reproduce the spontaneous symmetry breaking mechanism characteristic of these models, which in turn is responsible for the generation of dressed mass in a number of quantum many-body systems. |
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H71.00166: High-Fidelity, High-Scalability Two-Qubit Gate Scheme for Superconducting Qubits Yuan Xu, Ji Chu, Jiahao Yuan, Jiawei Qiu, Yuxuan Zhou, Libo Zhang, Xinsheng Tan, Yang Yu, Jian Li, Fei Yan, Dapeng Yu High-quality two-qubit gate operations are crucial for scalable quantum information processing. Often, the gate fidelity is compromised when the system becomes more integrated. Therefore, a low-error-rate, easy-to-scale two-qubit gate scheme is highly desirable. Here, we experimentally demonstrate a new two-qubit gate scheme that exploits fixed-frequency qubits and a tunable coupler in a superconducting quantum circuit. The scheme requires less control lines, reduces cross talk effect, and simplifies calibration procedures, yet produces a controlled-Z gate in 30 ns with a high fidelity of 99.5%, derived from the interleaved randomized benchmarking method. Error analysis shows that gate errors are mostly coherence limited. Our demonstration paves the way for large-scale implementation of high-fidelity quantum operations. |
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H71.00167: Lindbladian quantum error correction Oles Shtanko, Victor Albert Lindbladian-based autonomous error correction promises several advantages over traditional measurement-based schemes, including that it can be embedded directly in the computation, circumventing classical outer control. Building on previous work, we characterize Lindbladians designed for encoding information, error mitigation, or error correction. We provide several examples of how these types of Lindbladians can be implemented in the experiment. |
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H71.00168: Quantum inverse design with NISQ computers: applications in quantum sensing, imaging, and spectroscopy Cristian Cortes, Stephen Gray Inverse design is a computational paradigm that uses classical optimization algorithms to design classical devices with respect to user-defined performance metrics. This paradigm can be generalized to the quantum domain by replacing classical algorithms with quantum algorithms and replacing classical devices with quantum devices. In this talk, I will discuss how the inverse design problem is defined for quantum metrology with applications in quantum sensing, imaging, and spectroscopy. I will also present several variational quantum algorithms that aim to solve the inverse design problem via noisy-intermediate scale quantum (NISQ) computers. Our methodology adds to the list of potential applications for near-term quantum computers, while also presenting a new approach for quantum experimental design relevant to all sciences. |
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H71.00169: Strong exciton-photon coupling mediated by dephasing in site-controlled InGaAs quantum dots-nanocavities Wei Liu, Jiahui Huang, Eli Kapon, Chee Wei Wong In coupled solid-state quantum dot (QD)-cavity system, decoherence fundamentally affects coherent controll for quantum communication. Relying on our site-controlled single pyramidal InGaAs/GaAs QD – high Q photonic crystal cavities platform, we systematically investigate the cavity quantum electrodynamics in strong coupling regime mediated by cavity loss and the exciton pure dephasing. The single excitonic emission and cavity mode reveals anti-crossing with vacuum Rabi splitting around 50 µeV and typical averaging of QD-cavity luminescence at near resonance, which indicates strong coupling in our system. More importantly, as cavity loss is larger than pure dephasing rate, we observe linewidth averaging between cavity mode and exciton, which evidences the half-light-half-matter nature. Conversely, when the cavity linewidth is smaller enough and closed to that of exciton, their linewidths exhibit an mutual narrowing at near resonance. It indicates a strong surpression of pure dephasing of excitons owning to its half-photon signature in the strong coupling regime, allowing a less affect from the charge fluctuation and phonon scattering. |
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H71.00170: Reconstruction of the Band Structure of a 2D Lattice of Superconducting Resonators with Laser Scanning Microscopy Alexis Morvan, Mathieu Féchant, Gianluca Aiello, Julien Gabelli, Jerome Esteve Lattices of superconducting resonators hold the promise of providing a new platform for photonics lattices with sizable non linearity. In this letter, we describe the realization and study of honeycomb lattices of about 500 superconducting Nb spiral resonators. We image the lattice normal modes with a laser scanning technique. This allows us to reconstruct the lattice band-structure and density of states. Our results are in good agreement with ab initio electromagnetic simulations. As an example of a specially tailored lattice, we have designed a boundary between two honeycomb lattices with opposite mass imbalance (Semenoff insulators) and observe the edge states localized at the boundary. The existence of these states have a topological origin tied to the topological properties of the Dirac points in honeycomb lattices. |
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H71.00171: Generalized measure of quantum synchronization noufal Jaseem, Michal Hajdusek, Parvinder Solanki, Leong-Chuan Kwek, Rosario Fazio, Sai Vinjanampathy We present a generalized information-theoretic measure of synchronization in quantum systems. |
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H71.00172: Weak-value magnetometry for precision tests of fundamental physics Sounok Ghosh, Leong-Chuan Kwek, Daniel Terno, Sai Vinjanampathy Progress in testing fundamental physics relies on our ability to measure exceedingly small physical quantities. Using a trapped ion system as an toy model we show that an exceedingly weak synthetic magnetic field (at the scale of 10EXP-19T) can be measured with current technology. This improved sensitivity can be used to test the effects of spin coupling that affect the equivalence principle and, if present, may impact the performance of the proposed entangled optical clocks arrays. |
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H71.00173: Circuit QED system using Triple-Leg Stripline Resonator Kyungsun Moon, Dongmin Kim We theoretically propose a new circuit QED system implemented with a triple-leg stripline resonator (TSR). The fundamental intra-cavity microwave modes of the TSR are two-fold degenerate. When a superconducting qubit is placed near one of the TSR legs, one fundamental mode is directly coupled to the qubit, while the other one remains uncoupled. Using our circuit QED system, we have theoretically studied a two-qubit quantum gate operation in a hybrid qubit composed of a flying microwave qubit and a superconducting qubit. |
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H71.00174: DATA SCIENCE
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H71.00175: Small Data Enabled Prediction and Verification of Potential Polymer Membranes for CO2 Separation Hsianghan Hsu, Ronaldo Giro, Mathias Steiner, Toshiyuki Hama, Seiji Takeda
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H71.00176: A Novel Computational Artificial Intelligence Framework for Complex Physical, Chemical and Biological Networks Vishnu Shankar, Sadasivan Shankar We have designed and implemented an efficient chemical computing architecture and platform for simulating realistic chemical systems in conventional silicon processors. The architecture uses new logic (non-boolean), computing primitives, software architecture, and a new high-level programming language. This new framework adopts the advantages of conventional computing (access to large computing power) and will be optimized for computing of complex physical chemical or biological systems. |
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H71.00177: End-to-End Differentiability and Tensor Processing Unit Computing to Accelerate Materials’ Inverse Design Han Liu, Yuhan Liu, Mathieu Bauchy Simulations have revolutionized material design. However, although simulations excel at mapping an input material to its output property, their direct application to inverse design (i.e., mapping an input property to an optimal output material) has traditionally been limited by their high computing cost and lack of differentiability, so that simulations are often replaced by surrogate machine learning models in inverse design problems. Here, we introduce a computational inverse design framework relying on end-to-end differentiable simulations that addresses these challenges. Importantly, this pipeline leverages for the first time the power of tensor processing units (TPU)—an emerging family of dedicated chips, which, although they are specialized in deep learning, are flexible enough for intensive scientific simulations. |
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H71.00178: Machine Learning-Aided Development of Empirical Forcefields for Glasses Han Liu, Mathieu Bauchy The development of reliable, yet computationally-efficient interatomic forcefields is key to facilitate the modeling of glasses. However, the parameterization of novel forcefields is challenging as the high number of parameters renders traditional optimization methods inefficient or subject to bias. Here, we present a new parametrization method based on machine learning, which combines ab initio molecular dynamics simulations, Gaussian Process Regression, and Bayesian optimization. By taking the examples of silicate and chalcogenide glasses, we show that our method yields new interatomic forcefields that offer an unprecedented agreement with ab initio simulations. This method offers a new route to efficiently parametrize new interatomic forcefields for disordered solids in a non-biased fashion. |
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H71.00179: Machine learning topological phase transitions through local curvature Wei Chen, Antonio Zegarra, Evert van Nieuwenburg, Paolo Molignini, Ramasubramanian Chitra The topological order in materials is often calculated from the integration of a certain curvature function over the entire Brillouin zone. At topological phase transitions, the curvature function diverges and changes sign at certain high symmetry points in momentum space. These generic properties lead us to suggest a supervised machine learning scheme that uses only the curvature function at high symmetry points as input data to predict topological phase transitions. We use interacting models to demonstrate the efficiency of this method, which is shown to predict both the first- and second-order topological phase transitions caused by interactions with 100 percent accuracy in various models. The method further unveil the topological quantum multicriticality caused by many-body interactions. In particular, the electron-phonon interaction causes multicritical points where first- and second-order topological phase transitions intercept, and the first-order transition is accompanied by closing of the gap between the quasiparticle peak and the incoherent peak. |
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H71.00180: Fundamental Study of Solvated Crystal Structures Using Data-Mining and Machine-Learning Method Phu Nguyen For solvated crystals, the implications in material synthesis, molecular biology, environmental science (e.g. CO2 capture, metallurgy) and especially the pharmaceutical industry are enormous due to the effects in physicochemical properties of materials which in turn can influence the pharmaceutical synthesis steps during drugs manufacturing. For the formation of solvated crystals, the fundamental understanding remains elusive. To obtain an in-depth systematic study, a high-throughput screening of data-mining study of large dataset of solvated crystals might be useful. To achieve this goal, a dataset consists of organic, ionic and nonpolymeric molecules was extracted from the Cambridge Structural Database. In this study, we will share with you our findings in one particular types of solvates, i.e. dimethyl sulfoxide solvates based on several machine-learning models (e.g. random forest, gradient boosting, etc.). Based on or current models, the prediction of the behavior of ~ 80% of the data correctly using machine-learning model is attainable. |
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H71.00181: Fundamental Study of Ionic Liquids Melting Point Structure-Property Using Machine-Learning Method Zafer Acar, Michael Munje, Phu Nguyen, Kah Chun Lau For the application of ionic liquids (ILs), the intense interest has been due to the various novel properties, such as tunable ionic conductivity, negligible vapor pressure, liquid phase within a wide temperature range, non-flammability at ambient condition, etc. Among these properties, the melting point (Tm) of ionic liquid (IL) is very important in various applications. However, the (Tm) can change considerably depending on the molecular structures of the anion and cation. Recent years have seen a huge rise in the successful application of the machine or statistical learning type approaches to the discovery and in silico design of new novel materials. Deep-Learning algorithms can take structure-properties from extremely large data sets and use them to create a predictive tool based on hidden patterns and correlations. In this study, we will explore the use of various machine learning and deep learning methods to predict the melting points of various ILs that consist of several different cation and anion classes. From this preliminary study, we hope some important molecular descriptors that dictate the melting temperature of ionic liquids can be found, and subsequently can be used as new design rules. |
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H71.00182: Fast automated cross-platform cross-language parallel stochastic optimization, sampling, and integration with the ParaMonte library. Amir Shahmoradi, Shashank Kumbhare, Joshua Osborne, Fatemeh Bagheri ParaMonte (standing for Parallel Monte Carlo) is a serial as well as MPI/Coarray-parallelized library of (Markov Chain) Monte Carlo (MCMC) routines for sampling mathematical objective functions, the distributions of the posterior parameters of Bayesian models, and generic scientific inference problems in data science, Machine Learning. In addition to providing access to fast high-performance serial/parallel stochastic sampling routines, the ParaMonte library provides extensive post-processing and visualization tools that aim to automate and streamline the process of parameter estimation, uncertainty quantification, and model selection in Bayesian data analysis. Furthermore, the automatically-enabled restart functionality of ParaMonte samplers ensures a seamless fully-deterministic into-the-future restart of Monte Carlo simulations, should any interruptions happen. The ParaMonte library is MIT-licensed, cross-platform, and cross-language, currently available in C, C++, Fortran, MATLAB, Python, and R. The repository of the library is permanently maintained on GitHub at https://github.com/cdslaborg/paramonte. |
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H71.00183: COMPUTATIONAL PHYSICS
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H71.00184: Symmetry and Group Theory for Density-Functional Methods Kusal Khandal, Chandra B Shahi, Karma Dema, Zahra Hooshmand, Mark Pederson From the standpoint of performing quantum-mechanical calculations efficiently, describing the behavior of molecular- and cluster- based quantum devices, and effectively storing or processing quantum information, the use of symmetry or automated group theoretical methods offers significant advantages for researchers. Here we describe the development and use of an automated tool that determines the point-group symmetry of a molecule and then determines every sub-group and associated set of inequivalent atoms that describe the structure of the entire molecular system. To illustrate the utility of this tool, in conjunction with density functional theory, we present examples on developing efficient workflows for (1) the calculation of exchange-coupling parameters in inorganic molecular magnets (2) the determination of polarizabilities in the benzene molecule and (3) the calculation of infrared-active vibrations in methane. |
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H71.00185: PyFLOSIC - User-friendly Python implementation of the Fermi-Löwdin orbital self-interaction correction Kai Trepte, Sebastian Schwalbe, Jakob Kraus, Jens Kortus, Susi Lehtola There is an ongoing paradigm shift in computational science in |
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H71.00186: porE: Deterministic analysis of porosities in metal-organic frameworks Kai Trepte, Sebastian Schwalbe While analyzing periodic structures like metal-organic frameworks (MOFs), pores are an essential property |
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H71.00187: Scrambling in the memory matrix formalism; quantum information as a hydrodynamical slow mode. Ewan McCulloch, Curt von Keyserlingk Quantum information is conserved under unitary dynamics, and can be viewed as a hydrodynamical slow mode. We re-frame operator spreading within the memory matrix formalism (MMF) by including this often overlooked slow mode. This formalism yields a succinct expression for the butterfly velocity and shows that the biased diffusion of operators in ergodic systems is arguably the simplest scenario consistent with unitary dynamics. We use this formalism to present non-perturbative results for a Floquet circuit without symmetry and discuss the inplications of additional conserved quantities on scrambling. |
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H71.00188: Theoretical Study of Correlation of Sodium Cluster and NMR Analysis in Sodium-ion Rechargeable Batteries Ayane Suzaki, Azusa Muraoka, Koichi Yamashita The lithium ion batteries (LIB) which are a typical secondary batteries, is widely used as an energy storage system. However, due to problems with the resources and costs of lithium in LIB, there is a growing interest in resource-rich sodium-ion batteries (NIB) with equivalent electrode potential. In recent years, a NIB using a Na metal oxide as the positive electrode and hard carbon (HC) as the negative electrode has attracted attention in particular. To develop a NIB with high capacity, high efficiency, long life, and acceptable safety, it is essential to elucidate the state of the sodium ion and the mechanism of charge and discharge on the electrode. The states of sodium electrochemically inserted in HC samples have been experimentally reported using solid 23Na-NMR [1, 2]. In this study, in order to study the correlation of NMR shift of Na clusters with pore size in HC and structure and the electron density dependence of the 3s orbital, DFT calculations are performed at the level of B3LYP/6-31G(d) using the Gaussian 16. |
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H71.00189: Efficient approaches in DMFT for multi-degree-of-freedom systems Ryota Mizuno, Masayuki Ochi, Kazuhiko Kuroki Although several impurity solvers in DMFT[1] have been proposed, especially in multi-degree-of-freedom systems, there are practical difficulties arising from a trade-off between numerical costs and reliability. In this study, we re-interpret the iterative perturbation theory(IPT)[2] from the perspective of the frequency dependence, and extend it such that costs and reliability can be compatible. From the same perspective, we also develop the methods in which the dual fermion calculation[3] can be performed efficiently and can be combined with any impurity solver. We validate these methods by comparing them with several numerically exact methods. As a result, we confirm that the results of our methods show good agreements with that of the exact methods not only in single-degree-of-freedom systems but also in multi-degree-of-freedom systems. In the presentation, we explain the details of the methods, and show the results of benchmarks. |
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H71.00190: Dynamic local-field correction for the one-component plasma Hanno Kaehlert The density response function of the one-component plasma has important applications, e.g., in the calculation of stopping power or wave spectra. It can be expressed in terms of the dynamic local-field correction (LFC), which contains all effects that are not accounted for in a mean-field description. In this contribution, the complex response function and the dynamic LFC are computed from molecular dynamics simulations. The calculation is based on the fluctuation-dissipation theorem, which links the imaginary part of the response function to the dynamic structure factor, and the Kramers-Kronig relations, which is used to obtain the real part. |
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H71.00191: Characterizing Atomic Scale Strain Variations in 2D Materials with a Convolutional Neural Network Daniel Glazer, Kevin Honz, Riju Banerjee, Anna Binion, Eric Hudson Local measurements of electronic properties, enabled by scanning tunneling microscopy (STM), have led to a better understanding of 2D materials such as graphene and MoC2. The impact of local strain on these properties has been of great theoretical and experimental interest. However, correlating these electronic properties with local strain has proven challenging, as directly measuring strain - determining picometer-scale offsets of atoms from their unstrained locations – is non-trivial. Here we present the development of a convolutional neural network to assign atom locations and local strain values to STM topographies of hexagonal lattices. Our method enables the direct visualization of atomic-scale strain variations in Moiré patterns, doping impurities, and other similar structures. We will discuss future applications as well as improvement of model accuracy through increasingly realistic simulated training sets and better post-processing techniques. |
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H71.00192: Ab-initio simulations of the interactions of isolated defects Swarnava ghosh Interacting defects give rise to interesting phenomena such as nanovoid and prismatic dislocation loop formation through vacancy coalescence, precipitate nucleation through solute segregation, and solute diffusion through solute-vacancy binding. Though, ab-initio methods such as Density Functional Theory (DFT) is capable of capturing the chemical effects of the defect core, large cell sizes are required to accurately capture the elastic field arising from these defects. Popular DFT codes are cubic scaling with respect to the number of atoms and employ periodic boundary conditions, making accurate simulations of defect interactions difficult. We present an accurate and efficient finite-difference formulation and parallel implementation of Linear Scaling Kohn-Sham Density (Operator) Functional Theory (DFT) for non-periodic systems embedded in a bulk environment. We first discuss the parallel scalability of the framework, and then discuss the interactions of isolated defects in Mg-Al alloys. |
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H71.00193: First-Principles Modeling of the Kinetics of Electrochemistry at Solid-Water Interface Xunhua Zhao, Yuanyue Liu Kinetic information, such as the activation energy and transition state, is critical to understanding the reaction. However, the kinetic information of electrochemistry at solid-water interface is challenging to obtain from conventional models of density functional theory (DFT), as they often neglect the presence and/or the dynamics of the surface charge [1] and the solvent configuration, which are further coupled. Here we present a new model that accounts for these effects, by combining hybrid solvation, constant-electron-potential, and slow-growth sampling techniques together. We then apply this model to elucidate the active site structure and the mechanism of electrochemical carbon dioxide reduction catalyzed by single-nickel-atom embedded in graphene, which shows high performance in experiments while is not well understood [2]. |
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H71.00194: Towards inverse nanophotonic design by predicting plasmonic responses in nanoparticle assemblies with deep learning Kevin Roccapriore, Maxim Ziatdinov, Shin Hum Cho, Jordan A Hachtel, Sergei Kalinin Nanoscale structures designed with desired optical responses is a long sought-after goal of the photonics and materials science communities. Much progress has been made recently towards the inverse design challenge, particularly with several deep learning strategies, which was outlined in excellent detail1. Most of these routes, however, have been focused toward macroscopic or effective optical responses, while nanoscale spatial behavior has been overlooked. Emergent quantum technologies will heavily rely on optical effects at the nanoscale, thus appropriate design choice of nanophotonic elements in this regime is of critical importance. We develop here a deep learning strategy utilizing an encoder-decoder scheme applied to scanning transmission electron microscopy (STEM) monochromated electron energy loss spectroscopy (EELS) data. The nanoscale spatial resolution provided by the electron probe in EELS allows to decode the nanoscale design space, and together with the autoencoder networks, the correlative relationship between plasmonic spectra and geometry is established, ultimately allowing geometry prediction given spectral input (inverse design). |
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H71.00195: Field-controlled transport of Dirac particles with elliptical dispersion Paula Fekete, George Shuyi Zhang, Andrii Iurov, Godfrey Anthony Gumbs, Liubov Zhemchuzhna, Danhong Huang We investigate tunneling and transport properties of Dirac electrons dressed by a linearly-polarized, off-resonance, and high-frequency dressing field through graphene and dice lattice sheets. We employ Floquet-Magnus perturbation theory to obtain the quasiparticle energy dispersion relation and closed form analytic expressions for dressed electron wave functions. We illustrate how features of the anomalous Klein paradox, i.e., a complete, asymmetrical electron transmission, which is independent on the barrier height or width, is modified by the anisotropic energy dispersion caused by the applied dressing field. We investigate the current strength and its dependence on the asymmetry introduced by Klein tunneling. The relationship of transmission current peaks to Klein tunneling maxima is examined. We predict a decrease in transmission current when the Klein transmission peak is located at a larger angle. We expect larger transmission current in the dice lattice than in graphene due to a much broader Klein tunneling peak in the former system. Predicted transport properties are expected to be useful in the design of novel electronic and optical graphene-based devices and electronic lenses in ballistic-electron optics. |
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H71.00196: Static Density Response of the Warm Dense Electron Gas beyond Linear Response Theory: Excitation of Harmonics Maximilian Boehme, Tobias Dornheim, Jan Vorberger, Zhandos Moldabekov, Michael Bonitz Experimental setups as well as theoretical modeling of Warm Dense Matter (WDM) heavily rely on linear response theory. However, Dornheim et. al. [Phys. Rev. Lett.125, 085001 (2020)] showed that assuming the linear regime is not always justified for WDM. We use the ab initio Path-Integral Monte-Carlo (PIMC) technique to obtain exact results for a harmonic disturbed homogeneous electron gas. A thorough analysis for different perturbation amplitudes is carried out. The corresponding density response reveals resonances at the higher harmonics of the disturbance frequency. Furthermore, the induced density response as a function of the perturbation strength unveils that the dominant term beyond linear response is the second harmonic. The results signify the importance of response contributions beyond the linear regime to accurately model WDM. |
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H71.00197: Löwdin's Symmetry Dilemma in Correlated Systems: Green Functions Theory Results Sönke Hese, Jan-Philip Joost, Niclas Schlünzen, Michael Bonitz, Claudio Verdozzi, Peter Schmitteckert, Miroslav Hopjan The Hubbard model is a key system in the theory of strongly correlated electrons in solids, and it is realized with atoms in optical lattices. In the well-studied one-dimensional case, exact solutions are provided by analytic methods and density-matrix-renormalization-group (DMRG) simulations. In 2D and 3D, Green functions combined with many body approximations (GFMBA) present a reliable approach [1]. Here we present results demonstrating the capability of GFMBA to produce reliable data for the Hubbard gap energy despite its approximate character. We observed an improvement to the gap energy when lifting restrictions on spin symmetry and spatial homogeneity coupled with a spontaneous breaking of symmetry. This "symmetry dilemma" was described by Löwdin for Hartree Fock wave function calculations, and is extended here to GFMBA beyond Hartree-Fock [2]. |
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H71.00198: Ionization potentials and fundamental gaps in atomic systems from the ensemble-DFT approach Sharon Lavie KS-DFT is a potent and extensively used theoretical framework for quantum simulations. While exact in principle, it is approximate in practice. Many of the commonly used exchange-correlation approximations (xc) deviate from the exact requirement of piecewise linearity for the energy. Disobeying this requirement causes low predictive power of the eigenvalues; specifically, the ionization potentials (IP) and fundamental gaps are underestimated. We addressed this problem by applying the ensemble generalization treatment to the Hartree-xc energy functional[1]. This treatment proved beneficial in the restoration of the IP theorem and simultaneously reintroduction of the derivative discontinuity into any approximate xc functional in selected systems[2]. Here, I present a comprehensive study of IP and the electron affinity (EA) calculations from the ensemble-generalized KS energy levels, using the ensemble LSDA and the ensemble generalized PBE-GGA approximations to all atoms and first ions in the periodic table. Even with these simple functionals, the prediction of the IP and the EA can be significantly improved. Analyzing the accuracy of results obtained for the different periodic table blocks reveals interesting trends and provides valuable insights for future functional development. |
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H71.00199: Origin of Low Electron Mobility in Two-Dimensional Semiconductors Long Cheng, Chenmu Zhang, Yuanyue Liu Atomically thin (two-dimensional, 2D) semiconductors have shown great potential as the fundamental building blocks for next-generation electronics. However, all the 2D semiconductors that have been experimentally made so far have room-temperature electron mobility lower than that of bulk silicon, which is not understood. Here, by using first-principles calculations and reformulating the transport equations to isolate and quantify contributions of different mobility-determining factors, we show that the universally low mobility of 2D semiconductors originates from the high “density of scatterings,” which is intrinsic to the 2D material with a parabolic electron band. The density of scatterings characterizes the density of phonons that can interact with the electrons and can be fully determined from the electron and phonon band structures without knowledge of electron-phonon coupling strength. Our work reveals the underlying physics limiting the electron mobility of 2D semiconductors and offers a descriptor to quickly assess the mobility. [1,2,3] |
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H71.00200: Entropy scaling law and the quantum marginal problem Isaac Kim Quantum many-body states that frequently appear in physics often obey an entropy scaling law, meaning that an entanglement entropy of a subsystem can be expressed as a sum of terms that scale linearly with its volume and area, plus a correction term that is independent of its size. We conjecture that these states have an efficient dual description in terms of a set of marginal density matrices on bounded regions, obeying the same entropy scaling law locally. We prove a restricted version of this conjecture for translationally invariant systems in two spatial dimensions. Specifically, we prove that a translationally invariant marginal obeying three non-linear constraints -- all of which follow from the entropy scaling law straightforwardly -- must be consistent with some global state on an infinite lattice. Moreover, we derive a closed-form expression for the maximum entropy density compatible with those marginals, deriving a variational upper bound on the thermodynamic free energy. |
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H71.00201: Positivity Preserving Density Matrix Minimization for Finite and Zero Temperatures Jacob Leamer, Denys Bondar Knowledge of the density matrix is critical for understanding the dynamics of many materials. We present methods for calculating the Fermi-Dirac density matrix for electronic structure problems at both finite and zero temperature while preserving physicality. In either case, we consider both the grand canonical ensemble (constant chemical potential) and the canonical ensemble (constant number of electrons). The methods for calculating the finite temperature case are based around the minimization of the density matrix, while the methods for calculating the zero temperature case are based on self-consistent iterations. Our presented methods are able to calculate the density matrix with more accuracy than previous methods while still scaling linearly with the size of the system in question. |
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H71.00202: GTPack - a free Mathematica Group Theory Package Richard Geilhufe, Wolfram Hergert GTPack is a free Mathematica group theory package containing more than 200 additional group theory modules for the Mathematica language. GTPack builds a bridge between computational algebra, university education, and modern research, with wide-ranging applications in condensed matter and solid-state physics, photonics, and quantum chemistry. The poster will present latest developments and a current overview of the capabilities of the package. |
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H71.00203: Bottom-up Ultra-coarse-graining of Homopolymers for Inhomogeneous Systems Fabian Berressem, Christoph Scherer, Denis Andrienko, Arash Nikoubashman We coarse-grain homopolymers into single spheres, focusing on simulations of thin films and droplets. Accurately representing these inhomogeneous systems by a coarse-grained (CG) model is a difficult task due to the large density variations at the interfaces. Using CG models interacting only via pair potentials parametrized in the bulk leads to unstable systems, because the surface tension is not preserved. We follow an alternative approach, including higher order interactions either through an additional three-body potential or a local density-dependent potential. We parametrize the two- and three-body potentials via force matching, and the local density-dependent potential through relative entropy minimization. While the CG models with three-body potentials fail to reproduce stable polymer films and droplets, CG simulations with a local density-dependent potential are able to do so. A detailed analysis of the film/droplet morphologies reveals some (minor) quantitative differences between the reference and the CG simulations, namely a slight broadening of the interfaces accompanied by a smaller surface tension in the CG simulations. These differences are due to the deformation of polymers near the interfaces, which can not be resolved in the CG representation. |
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H71.00204: Can we study warm dense matter using density matrix quantum Monte Carlo? A study of the sign problem and molecular hydrogen chains. Hayley Petras, William Van Benschoten, Sai Kumar Ramadugu, James Shepherd Finite temperature electronic energies play a role in understanding warm dense matter. The recently developed density matrix quantum Monte Carlo (DMQMC) method can be used to obtain exact-on-average finite temperature energies. The fermion sign problem exists for DMQMC much like the full configuration interaction quantum Monte Carlo method (FCIQMC), which it is related to. We perform a systematic study of the sign problem in DMQMC using Hn chains, where n = (4,6,8,10). This systematic study looks at a range of walker populations and the resulting energies for each system. In doing so, we probe the impact the sign problem has in DMQMC. We also investigate how the simulation variables and the sign problem are related by measuring the plateau heights of the hydrogen chains previously mentioned. |
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H71.00205: Theoretical Predictions of Superconducting Properties of Ternary Hydrides Under Pressure Morgan Redington, Nisha Geng, Eva Zurek When studying pressure-induced superconductivity, hydrogen stands out over other elements. Several binary alkaline and rare earth metal hydrides that assume hydrogenic clathrate systems have been predicted to posess high critical temperatures. Computational results from a ternary hydride incorporating lithium and magnesium suggested a critical temperature far above room temperature, but other mixed alkali/alkaline earth metal ternary hydrides are unexplored. Utilizing the XtalOpt evolutionary algorithm for crystal structure prediction novel superconducting ternary hydrides were discovered at experimentally attainable pressures. These systems were investigated using first-principles calculations, elucidating electronic structure, stability, and additional properties. |
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H71.00206: Effect of Parameter Choice in Density Functional Perturbation Theory Calculations of Phonons and Related Properties Ryan Glusic, William Parker In atomic matter, phonon modes and frequencies determine material properties such as thermal and electrical conductivity. Allowed vibrational frequencies are found by solving a characteristic equation for the dynamical matrix constructed through the second derivatives of energy with respect to displacements of the atoms. One method for effecting quantum mechanical solutions in this context is density functional perturbation theory (DFPT). In this method, the electron density is calculated by solving a mean-field Hamiltonian self-consistently for the its energy and wave functions, keeping the atoms at their relaxed positions. Then, the perturbation in energy with respect to perturbations of the atoms is calculated for every unique atomic displacement combination. DFPT has multiple parameters to control for to produce realistic simulations. We investigate the effects of varying these parameters on the resulting phonon frequencies in terms of the relative and absolute error from a highly convergent phonon frequency using several electronically distinctive solid-state systems. We take the same approach to compare calculated with experimentally determined phonon frequencies, aiming to provide advice in choosing parameters for accurate DFPT calculations. |
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H71.00207: Structural and electronic properties of titanium nitride small nanocluster geometries Purbajyoti Bhagowati, Munima Sahariah Titanium nitrides (TiN) hold the characteristics of alternatives to the noble metals in the field of plasmonics. The bulk TiN has been studied rigorously both experimentally and theoretically by the researchers, but no reports on small TiN nanocluster geometries to the best of our knowledge. Nanoclusters are lower-dimensional structures possessing exciting properties. They are highly reactive compounds whose properties change with a slight change in composition or concentration. Here we have determined the low energy geometries of TiN nanocluster systems with the help of ab-initio molecular dynamics (AIMD) and thereafter studied their electronic properties. All the calculations were carried out using Vienna ab-initio simulation package (VASP) in the domain of density functional theory (DFT). |
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H71.00208: Electronic and magnetic properties of Mn-Pt-Sn inverse Heusler compound Payal Saha, Munima Sahariah For the applications in non-volatile memory technologies, the demand for new advanced magnetic materials is gradually increasing. Many experimental and theoretical studies prove that high perpendicular magnetic anisotropy is a much-needed parameter of a prospective material for applications in spintronic devices. The materials which show non-collinear magnetism are suitable for these purposes. Heusler alloys are famous for their tunable electronic and magnetic properties and according to some studies, Mn-based Heusler compound shows non-collinear magnetism. So, here we carry out the ab initio study on Mn-Pt-Sn inverse tetragonal Heusler compound based on Density functional theory using the software Vienna Ab-initio Simulation Package (VASP). This work focuses on different magnetic structures of Mn-Pt-Sn Heusler compound. |
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H71.00209: Candidate Planck (hc) Electrostatic Equations With Split Strength Constant (1/α) as Scaling Factor (r/α2) for Potential, (r/α)2 for Force as Particle Radius Versus the Bohr Radius Distance Ratio Square Root Defines ‘Charge’ Arno Vigen I examine the first fundamental force, electrostatic force, using my candidate equation to describe physical model underlying the proportionality, splitting abstract constants into a) a field strength constant part as (1/α), and b) field scaling factor, re-engineered as the potential equation scaling at 1/(r/α2), but force scaling at 1/(r/α)2 and field scaling at 1/(r/α)3: |
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H71.00210: Detecting confinement-deconfinement phase transition in disorder toric code using Spectrum Bifurcation Renormalization Group Hong-Ye Hu, Yizhuang You Randomness is common in nature and it could quantitatively change the behavior of the system, and critical universality class. Here, we generalize the spectrum bifurcation renormalization group (SBRG) method to the two dimensional strong disorder system. We first numerically calculated 2D Ising model in the strong disorder limit, and we find the phase transition point and critical exponent are consistent with the previous strong disorder renormalization group calculation. Next, we applied our method to the 2D toric code model in strong disorder limit. We showed that long range mutual information can be served as an indicator of the confinement-deconfinement phase transition. |
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H71.00211: Electronic correlation effects in the stopping power of ions in 2D materials Franziska Reiser, Lotte Borkowski, Niclas Schlünzen, Jan-Philip Joost, Michael Bonitz The energy loss of charged projectiles in correlated materials is of prime relevance for plasma-surface interaction for which we have developed a nonequilibrium Green functions (NEGF) approach. A particularly interesting effect is the correlation induced increase of stopping power at low velocities [1]. However, NEGF simulations are possible only for short time durations, due to the unfavorable Nt3 scaling with the number of discretization time steps. The situation has changed radically with the recently developed G1-G2 scheme [2], which is based on the generalized Kadanaoff-Baym ansatz in combination with Hartree-Fock propagators, and allows to achieve linear scaling with Nt. This enhancement enables us to improve previous simulations by using better selfenergies [3], studying larger systems and by extending the simulation duration which gives access to slower projectiles. Finally, we will report further improvements of the G1-G2 scheme itself, by taking into account three-particle correlations. |
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H71.00212: Computational Synthesis of MoS2 layers assisted by H2S Precursors Sungwook Hong, Ken-ichi Nomura, Rajiv K Kalia, Aiichiro Nakano, Priya Vashishta Layered transition metal dichalcogenides (TMDCs) like MoS2 layers are promising materials for next-generation electronic applications. Large-area monolayer MoS2 samples for these applications are typically synthesized by chemical vapor deposition (CVD) using MoO3 reactants and sulfur precursors. Recent experimental and computational studies have greatly improved our understanding of reaction pathways in CVD synthesis. However, effect of different types of sulfur precursor on CVD synthesis of MoS2 layer has yet to be fully investigated. Here, we present quantum-mechanically informed and validated reactive molecular dynamics (RMD) simulations to investigate CVD synthesis of MoS2 layer using S2 and H2S molecules. Our goal is to clarify the different sulfidation and reduction rates of MoO3 surface by S2 and H2S precursors. |
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H71.00213: Bond energies of molecules using optimal transport theory for the strictly-correlated-electron (SCE)
limit of Density-Functional-Theory Kshiteej Deshmukh, Kaushik Dayal Standard Kohn-Sham DFT starts from a mean-field approximation: the kinetic energy is modeled exactly, while the electron-electron interactions are modeled through a split into a mean-field term, and corrections from the exchange-correlation term. The SCE limit starts from the opposite limit: the electron-electron interactions are assumed to dominate over the kinetic energy, and hence it is a semi-classical limit. It is hence well suited to study strongly-correlated situations, e.g. bond breaking. While the SCE limit includes many-body interactions, it can be identified as a problem from Optimal Transport theory with Coulomb cost function. Hence it can be solved by a nested optimization in its dual (Kantorovich) formulation. We incorporate the Kantorovich solution within the KS-DFT framework and solve it using the finite element method. Bond-energy curve is obtained using this method for hydrogen molecule, and is compared against other exchange-correlation models to show the improved results. We then investigate bond-breaking in ethane and other small molecules using the SCE limit. |
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H71.00214: Geometric Relationship between Bose Cylinders and Slater Type Orbitals with Special Case for Gaussian Arno Vigen The Bose cylinder logic has become significant core concept in statistical mechanics. This presentation explores the understanding of the Bose cylinder as a cylinder of two groups at the same inclination/longitude of electrons in the same subshells in two hemispheres (“seems magnetic” 2) relative to the as a multi-particle set, specifically, a full subshell. |
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H71.00215: Geometric and Mathematical Relationship between Bose Cylinders and Slater Type Orbitals and a Special Case for Gaussian Two Poles Arno Vigen The application of the Bose cylinder logic has become significant core concept in statistical mechanics. This presentation explores the understanding of the Bose cylinder as a cylinder of two groups at the same inclination/longitude of electrons in the same subshells in two hemispheres (“seems magnetic” 2) relative to the as a multi-particle set, specifically, a full subshell. |
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H71.00216: Nucleon-nucleon interactions in a three-dimensional momentum helicity representation Mohammadreza Hadizadeh, Farzaneh Nazari, Mahdi Radin Partial wave (PW) decomposition approaches have been widely used in the few-body calculation. After truncation, a PW representation leads to coupled equations on angular momentum quantum numbers. The complexity of modern few-nucleon interactions with a different spin, isospin, and angular momentum combinations, demands avoiding a partial wave representation completely and working directly with vector variables by replacing the discrete angular momentum quantum numbers with continuous angle variables. Such a non-PW method is called a three-dimensional (3D) approach. To this aim, the nucleon-nucleon (NN) interactions are formulated in momentum-helicity basis states and obtained by adding the corresponding partial wave components to a desired total NN angular momentum. In our numerical study, the matrix elements of CD-Bonn potential are calculated in a 3D scheme and tested for deuteron binding energy and neutron-proton scattering. The 3D form of CD-Bonn interaction reproduces the PW results with very high accuracy and are in excellent agreement with experimental data. |
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H71.00217: Border effect in the Cr2Ge2Te6 nanoribbons: a stability study through Density Functional Theory Valeria Ríos Vargas, Rodrigo Ponce, María Guadalupe Moreno Armenta, Jonathan Guerrero Sanchez The Cr2Ge2Te6 compound is an intrinsic ferromagnetic material with a van der Waals layered structure that shows great promise in spintronic applications. In this work, we investigated the edge effect in the formation of Cr2Ge2Te6 nanoribbons with different edges as well as the change in electronic and magnetic properties, by spin-polarized calculations. We study the thermodynamic stability of the nanoribbon employing the surface formation energy formalism. According to the calculations, at Ge- and Te-poor conditions and Ge-poor Te-rich conditions, the nanoribbon terminated in Te-Cr is the most stable structure, also, at the limits Te- and Ge-rich conditions and Ge-rich Te-poor conditions, the most stable structure corresponds to a combination of Cr-Te and Te-Ge edges. |
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H71.00218: Tuning the thermoelectric Power Factor and exciton binding energy of monolayer group-III nitrides through alloying Daniel Wines, Fatih Ersan, Can Ataca Two-dimensional (2D) group-III nitride semiconductors (h-BN, h-AlN, h-GaN, and h-InN) have attracted attention due to their desirable electronic, optical, and thermoelectric properties. We performed density functional theory (DFT) calculations to investigate 2D B1-xAlxN, Al1-xGaxN, and Ga1-xInxN structures and assess how alloying impacts the material properties. In addition, we calculated the thermoelectric properties of these structures using Boltzmann transport theory based on DFT and the optical properties using the GW method and the Bethe–Salpeter equation. We find that by changing the alloying concentration, the band gap and exciton binding energies of each structure can be tuned accordingly, and for certain concentrations, a high thermoelectric performance is reported. In addition to confirming the dynamical stability of these alloys through phonon calculations, we treated the electron relaxation time rigorously using Deformation Potential Theory (DPT) and obtained an accurate estimate for the thermoelectric power factor. With the ability to engineer these properties by alloying 2D group-III nitrides, we believe that this work will play an important role for experimentalists focusing on next-generation electronic, optoelectronic, and thermoelectric devices. |
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H71.00219: Ab initio predictions of electronic, structural, mechanical, phonon, and optical properties of the Zr2GaC and Hf2GaC MAX phases under high pressure Muhammad Waqas Qureshi, Xinxin Ma, Ramesh Paudel The structural stability, electronic, mechanical, phonon, and optical properties of M2GaC (M = Zr, Hf) MAX phases have been investigated using first-principles calculations under high pressure. It is found that the compressibility of Zr2GaC is better than that of Hf2GaC along the c-axis, and pressure enhanced the resistance to deformation. The electronic structure calculations indicated that M2GaC is metallic, and the metallicity of Zr2GaC increased more than that of Hf2GaC at higher pressure. Moreover, mechanical properties, including elastic constants, elastic moduli, Vickers hardness, Poisson’s ratio anisotropy index, and Debye temperature, are reported under high pressure. It is observed that C11 and C33 increases rapidly compared with other elastic constants with an increase in pressure, and elastic anisotropy of Hf2GaC is higher than that of the Zr2GaC. Formation energy, elastic constants, and phonon calculations revealed that both compounds are thermodynamically, mechanically, and dynamically stable. Finally, optical properties revealed that Zr2GaC and Hf2GaC MAX phases are suitable for optoelectronic devices in the visible and UV regions and can also be used as a coating material for reducing solar heating at higher pressure up to 50 GP. |
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H71.00220: First-principles study of CuInP2S6 based van der Walls heterostructure at non-equilibrium state Yumin Song, Juho Lee, Yong-Hoon Kim The discovery of polarization switching in two-dimensional (2D) van der Waals (vdW) materials such as copper indium thiophosphate (CuInP2S6) has led to the development of ultrathin ferroelectric devices. However, the atomistic-level description of the switching process is still mostly limited to equilibrium first-principles methods, thereby lacking a direct connection to the experimental measurements. In this presentation, carrying out the recently developed multi-space constrained-search density functional theory (MS-DFT) [1], we study the polarization switching mechanism of CuInP2S6 on the electrified electrode surface under a finite bias. Taking the advantages of MS-DFT in which total energies are variationally calculated under finite-bias, we quantitatively provide the bias-dependent free energy and polarization profile by calculating the electric enthalpy. We also calculate the quantum transport properties of the vdW heterostructure composed of CuInP2S6 as a channel material sandwiched by various electrode materials and provide design guidelines for the development of advanced ferroelectric material-based nanodevices. |
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H71.00221: High responsivity in ReS2-based optoelectronic devices: A first-principles study Ryong Gyu Lee, Tae Hyung Kim, Yong-Hoon Kim Rhenium disulfide (ReS2), a member of the group-VII transition metal dichalcogenides (TMDs) family, has attracted attention for applications of optoelectronic devices with its exotic properties, such as the optical anisotropy and weak interlayer coupling. Experimental studies reported that ReS2-based phototransistors exhibit high responsivity, which is a crucial requirement for photodetector devices, but its origin has not been systematically studied yet. In this presentation, based on the combined density functional theory (DFT) calculation and the delta self-consistent field (ΔSCF) method, we investigate optical excitation behaviors of possible single-atom vacancies in monolayer ReS2. Since the classical ΔSCF scheme has limited applicability within the localized systems, we newly establish extended formalism to be utilized in general solid systems. Using the developed ΔSCF method, we present optical excitation process in the monolayer ReS2 and observe the formation of trapped electrons below conduction band. Our study provides theoretical background for applications of ReS2-based optoelectronic devices as well as the new methodology within the DFT for treating the optical excitation in general systems. |
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H71.00222: Ab-initio investigation of electronic excitations in bulk V2O5 Vitaly Gorelov, Matteo Gatti, Lucia Reining We present an ab-initio investigation of electronic excitations in bulk V2O5. Time-dependent Density-Functional Theory (TDDFT) calculations were performed to obtain the dielectric function within the linear response. When crystal local field effects are included, we find a quantitative agreement between theoretical and experimental electron energy loss spectra (EELS) for all the momentum transfers considered in the experiment [1]. The observed anisotropy of the EELS is analyzed. We also discuss photoemission and optical spectra including corrections from Many-Body Perturbation Theory. |
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H71.00223: A detailed Sensitivity Analysis of the Human Ventricular Cell Model in one-dimensional and two-dimensional tissue using GPU computing. Kamal Sharma, Abouzar Kaboudian, Flavio Fenton, Elizabeth Cherry Ventricular Arrhythmia is the leading cause of sudden cardiac death in the world. One goal of the CiPA initiative, sponsored by the FDA, is the in-silico quantification of the proarrhythmic effects of drugs. CiPA has selected the human ventricular model developed by O’Hara et al. (OVVR) as the most complete model to be used. So far, single-cell dynamics has been the focus of the study due to the computational complexity of the OVVR model (61 differential equations per cell to simulate 12 ionic currents). However, single-cell results do not translate to the 2D tissue behavior, where the coupling between cells induces emergent behavior like reentrant spiral waves. We present the first sensitivity analysis of the OVVR model in tissue computed using our WebGL library (Abubu.js) for simulation of 1D tissue faster than real-time, and of 2D tissue in near-realtime, without the need for a supercomputer. We quantify the dynamics in 1D by calculating action potential duration (APD) and conduction velocity (CV) restitution curves as we vary the parameter of the model. Surprisingly, we found a marginal effect on the APD restitution or the CV restitution for most currents. We conclude with a study of spiral-wave dynamics for the relevant parameters in 2D. |
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H71.00224: Multiple relaxation times in the Gibbs Ensemble Monte Carlo simulation of phase separation Bina Kumari, Subir Sarkar, Pradipta Bandyopadhyay
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H71.00225: Anomalous behavior of the electronic transport properties in thermoelectric materials due to electron-phonon interaction Natalya Fedorova, Andrea Cepellotti, Boris Kozinsky In this work we employ ab initio calculations to investigate the effects of the electron-phonon interaction on the transport properties of thermoelectric materials, focusing on the example of half-Heusler semiconductors. We calculate electron-phonon scattering rates using Wannier-Fourier interpolation of electron-phonon matrix elements and the recently developed electron-phonon averaged approximation. We find that the electron-phonon scattering can lead to anomalous behavior of the transport coefficients, namely the conductivity decreases with increasing number of charge carriers, and Seebeck coefficient changes sign, leading to an unusual peak in the power factor at high carrier concentrations. We discuss the origin and magnitude of this enhancement effect starting from the electronic band structure and identify design rules to maximize the material's performance. |
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H71.00226: Open System Tensor Networks and Kramers’ Crossover for Quantum Transport Gabriela Wojtowicz, Justin Elenewski, Marek Rams, Michael Zwolak Tensor networks are a powerful tool for many–body ground states with limited entanglement. These methods can nonetheless fail for certain time–dependent processes such as quantum transport or quenches. Matrix-product-state decompositions of the resulting out-of-equilibrium states require a bond dimension that grows exponentially, imposing a hard limit on simulation timescales. However, in the case of transport, if the reservoir modes of a closed system are arranged according to their scattering structure, the entanglement growth can be mitigated. Here, we apply this ansatz to open systems via extended reservoirs that have explicit relaxation. This enables transport calculations that can access steady states, time dynamics and noise, and periodic driving (e.g., Floquet states). We demonstrate the approach by calculating the transport characteristics of an open, interacting system. |
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H71.00227: Generating Synthetic XPS spectra for Neural Network Quantification of RHEED Data of Complex Oxides Michael Demos, Sydney Provence, Rajendra Paudel, Ryan B Comes, Giovanni Drera Neural networks are computational systems that rely on a series of weighted algorithms to processes input data and give an output. A common type of neural network used for image processing is a convolutional neural network (CNN). Due to their effectiveness at image classification, CNN’s have great potential to be useful in analysis of reflection high energy electron diffraction (RHEED) patterns of complex oxides. This potential is realized by creating a CNN that takes RHEED images as input and outputs a predicted x-ray phtotoelectron spectroscopy (XPS) spectrum of the material. Neural network performance depends on the weight values of the network, which are found by training the neural network. A problem that arises when training such a CNN is the limited availability of consistent XPS spectra to compare to the output of the neural network when training. This problem is overcome by using BriXias software to simulate a wide variety of XPS spectra. BriXias software utilizes a database of material characteristics to evaluate the inelastic mean free path (IMFP) and transport mean free path (TMFP) of electrons traveling within a material. It then uses the IMFP and TMFP, along with specified model parameters and XPS geometry, to simulate XPS data of material. |
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H71.00228: Efficient and Flexible Approach to Simulate Low-Dimensional Quantum Lattice Models with Large Local Hilbert Spaces Thomas Koehler, Jan Stolpp, Sebastian Paeckel Quantum lattice models with large local Hilbert spaces emerge across various fields in quantum many-body physics. Problems such as the interplay between fermions and phonons, the BCS-BEC crossover of interacting bosons, or decoherence in quantum simulators have been extensively studied both theoretically and experimentally. In recent years, tensor network methods have become a successful tool to treat such lattice systems numerically. Nevertheless, systems with large local Hilbert spaces remain challenging. Here, we introduce a mapping that allows to construct artificial U (1) symmetries for any type of lattice model. Exploiting the generated symmetries, numerical expenses that are related to the local degrees of freedom decrease significantly. Based on an intimate connection between the Schmidt values of the corresponding matrix-product-state representation and the single-site reduced density matrix, this allows for an efficient treatment of systems with large local dimensions. We demonstrate this new mapping, provide an implementation recipe, and perform example calculations for the Holstein model at half filling. We studied systems with a very large number of lattice sites up to L = 501 while accounting for N ph = 63 phonons per site with high precision in the CDW phase. |
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H71.00229: Predicting the atomic structure of magnetic layered materials from ab-initio materials simulations and machine learning Akram Ibrahim, Daniel Wines, Can Ataca A reliable soft chemical method has been developed to synthesize an air-stable layered material HxCrS2, which can be exfoliated down to ultrathin layers, providing the promise for synthesizing two-dimensional magnets1. However, the atomic structure of HxCrS2 is still unknown. We used a combination of density functional theory (DFT), ab-initio molecular dynamics (AIMD) and cluster expansion to study the energetics of HxCrS2 as a function of Cr vacancies and H impurities. Then, we investigated the stability, electronic and magnetic properties and examined the effect of layering on the investigated properties. We further applied different strains at different temperatures on the structures to generate a dataset of diverse local atomic environments for machine learning (ML). We used Gaussian processes and neural networks to fit a model for the potential energy surface (PES) of HxCrS2. After that, we implemented this potential model in classical molecular dynamics (MD) to be able to study more properties for macroscale structures of HxCrS2 to benchmark with available experimental data. This study represents a novel method of predicting the atomic structures of macroscale slabs with quantum mechanical accuracy. |
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H71.00230: Breaking the entanglement barrier: Tensor network simulation of quantum transport Marek Rams, Michael Zwolak The recognition that large classes of quantum many-body systems have limited entanglement in the ground and low-lying excited states led to dramatic advances in their numerical simulation via tensor networks. However, global dynamics elevates many particles into excited states, and can lead to macroscopic entanglement and the failure of tensor networks. Here, we show that for quantum transport - one of the most important cases of this failure - the fundamental issue is the canonical basis in which the scenario is cast: When particles flow through an interface, they scatter, generating a 'bit' of entanglement between spatial regions with each event. The frequency basis naturally captures that - in the long-time limit and in the absence of inelastic scattering - particles tend to flow from a state with one frequency to a state of identical frequency. Recognizing this natural structure yields a striking increase in simulation efficiency, greatly extending the attainable spatial- and time-scales, and broadening the scope of tensor network simulation to hitherto inaccessible classes of non-equilibrium many-body problems. |
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H71.00231: Accelerated Discovery of Polyetherimide based Dielectric Polymers using Graph Attention Neural Networks Ankit Mishra, Pankaj Rajak, Abdullah Alamri, Ajinkya Deshmukh, Ken-ichi Nomura, Gregory Sotzing, Rampi Ramprasad, Yang Cao, Aiichiro Nakano, Rajiv K Kalia, Priya Vashishta Polyetherimide (PEI) family of polymers popularly referred as ULTEM polymers are an important class of polymers which exhibit excellent thermal and mechanical properties and are widely used in producing high temperature films for capacitor applications. The properties of PEI can be greatly enhanced by modifying its backbone with various chemical, physical and structural defects along with various endcap substitutions. The large number of defects and substitutions generate a combinatorial large design space, which is difficult to explore using |
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H71.00232: Electronic and Optical Properties of Ag2Se Quantum Dots as Obtained via Quantum Calculations Nav Nidhi Rajput, Maxim Makeev, Michael Scimeca, Shlok Joseph Paul, Ayaskanta Sahu Quantum dots are of interest as optically-active elements for use in optoelectronic devices. Herein, we report on a combined experimental and theoretical study of Ag2Se quantum dots (QDs). Experimentally, we have observed a size-dependent phase transition from an orthorhombic crystal phase in the bulk to a metastable tetragonal phase for crystallites below 40-nm in size. The theoretical studies are performed on finite-sized nanocrystals using a linear response theory within the time-dependent local density approximation, as implemented in VASP package. The calculated parameters include the absorption spectra, optical band gaps, ionization and transition energies of the tetragonal phase. All the electronic and optical properties are computed for QDs with varying sizes, and the effect of size on the resulting properties is analyzed. Theoretical data are compared with the experimental results obtained on disordered arrays of Ag2Se QDs. |
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H71.00233: Neural Network Molecular Dynamics of SiSe2 Nitish Baradwaj, Aravind Krishnamoorthy, Ken-ichi Nomura, Aiichiro Nakano, Rajiv K Kalia, Priya Vashishta The structures of SixSe1-x, glasses with 0.0 < x < 0.40 have been investigated with neutron diffraction and Se K-edge extended X-ray absorption fine-structure measurements. Neural network MD (NNAIMD) is an emerging approach to study large-scale atomistic systems |
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H71.00234: Numerical Linked-Cluster Expansion Implemented Using igraph Jyoti Rani, Ehsan Khatami Numerical linked-cluster expansions have been used to study exact finite-temperature properties of quantum lattice models in the thermodynamic model. The algorithm involves identifying unique clusters that can be embedded in a lattice, their symmetries, and other properties. Here, we demonstrate that the method can be implemented efficiently in Python using the igraph package. We extend the application to lattice geometries with more than one type of bond and study the thermodynamic properties of the Ising model with next-nearest-neighbor interactions. |
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H71.00235: Predicting the stability and electronic properties of alkali-ion metal aurides Axel Gaona-Carranza, Jonathan Guerrero Sanchez, Reyes García-Díaz, Jesus María Siqueiros Beltrones
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H71.00236: SHOCK COMPRESSION OF CONDENSED MATTER
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H71.00237: Pressure Induced Emergence of Visible Luminescence in Lead Free Halide Perovskite Cs3Bi2Br9: Effect of Structural Distortion DEBABRATA SAMANTA, Pinku Saha, Bishnupada Ghosh, Sonu Pratap Chaudhary, Sayan Bhattacharyya, Swastika Chatterjee, Goutam Dev Mukherjee In recent years, halide perovskites of the formula A3B2X9 (A:Cs, Rb; B:Sb or Bi; and X:halogen) have been in research forefront due to their potential applications in optoelectronic devices and solar cells. We have carried out high pressure x-ray diffraction, Raman spectroscopy and photoluminescence measurements on a model Pb-free solar cell material Cs3Bi2Br9 halide perovskite, which is nonluminescent under ambient conditions. The sample starts showing photoluminescence above 1.4 GPa, due to an isostructural transition to a distorted unit cell. Further enhancement in intensity with pressure is found to be driven by increase in distortion of BiBr6 octahedra. Electronic band structure calculations show the sample in the high pressure phase to be an indirect band gap semiconductor. The photoluminescence peak shows a kink at higher energy and a broad asymmetric peak at lower energies due to the recombination of free excitons and self trapped excitons, respectively. |
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H71.00238: First principles study of the phase diagram of beryllium at terapascal pressures Jizhou Wu, Felipe Gonzalez, Burkhard Militzer Beryllium, a metal that is widely used in space science, plasma physics, and nuclear science, has triggered many investigations of its equation of state over past decades. It is used as an ablator material in internal confinement fusion and a gasket in diamond anvil cell where it will be exposed to megabar pressures. At high pressure, it transforms to a body centered cubic (bcc) structure, with negative Clapeyron slope. Here we present results from ab initio computer simulations of solid and liquid beryllium in combination with a thermodynamic integration technique to derive Gibbs free energies. We study the h.c.p., b.c.c., and liquid phases, exploring anharmonic effects and make predictions for the phase boundary under extreme conditions. |
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H71.00239: The Radiation effect observation on core-shell Ti@TiO2 by molecular dynamics simulation Mohammad Zahidul Khan Nanoparticles have been an area of active research in recent years due to their properties, which can be greatly different from the bulk. The core-shell nanomaterials and nanostructures have become an important research area since a few decades due to their potential applications in various fields like catalysts, industrial and biomedical applications, and radiation detection application. In this work, the radiation effect on core-shell Ti@TiO2 nanoparticles has been studied by using molecular dynamics simulations. A series of several cascades for each neutron recoil energy (50 keV, 100keV, 150keV, 200keV and 250 keV) have been simulated to assure statistical precision. Also, for observing the temperature effect, three different temperature (100 K, 300 K and 500 K) have been used for each recoil energy. Radiation energy generates the point defects inside the core-shell nanoparticles (NPs) and all the defects accumulate near the core and shell interface and also the surface of the NPs. It is also observed that core remain almost intact after the irradiation but its mean square displacement change with changing the radiation energy. |
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H71.00240: Compression of Heavy Alkali Metals at Multi-Megabar Pressures Christian Storm, Sarah Finnegan, Edward Pace, Michael Stevenson, James McHardy, Simon MacLeod, Malcolm McMahon The light alkali metals are of particular interest to both experimental and theoretical investigations due to their exotic behaviour at extreme conditions, and relative atomic simplicity facilitating ab initio analysis using DFT and MD simulation. While considered simple elements at ambient conditions, well-described by the free-electron model, these metals become increasingly complex at extreme conditions; |
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H71.00241: Three-dimensional radiation hydrodynamic simulations of laser-produced air plasma - aluminum slab interaction Sai Shiva Sakaraboina, Prem Kiran Paturi, Venkata Ramana Ikkurthi The interaction of laser-produced hot air plasma with a solid aluminum target and the subsequent shockwave (SW) dynamics in the target is studied using the three-dimensional FLASH Eulerian radiation hydrodynamic (3D-RHD)1,2 numerical simulations performed in the Cartesian geometry. The high-temperature air plasma to Al target distance was taken as 1 mm. The air plasma is generated by focusing a laser pulse of 10 ns with energies 0.2 – 0.5 J at 532nm to a spot diameter of 500 µm. The rapidly expanding forward-moving plasma interacts with the Al slab resulting in the reflection of the plasma and launches SW onto the target surface. The reflected plasma accelerated the steep expansion of the plasma along the laser propagation direction. The evolution of SW was analyzed for different laser intensities. |
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H71.00242: Metallization of dense fluid helium from ab initio simulations Martin Preising, Ronald A. Redmer Previous studies [Preising et al., Phys. Plasmas 25, 012706 (2018); Preising et al., Phys. Rev. B. 100, 184107 (2019)] allowed for the consistent examination of the metallization of fluid helium with DFT-MD. |
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H71.00243: Atomistic Predictions of Reaction Mechanisms, Kinetics, and Detonation Properties for the Insensitive Explosive LLM-105 Brenden Hamilton, Brad Steele, Michael Sakano, Matthew Kroonblawd, I-Feng W Kuo, Alejandro Strachan Understanding the mechanical and chemical characteristics of insensitive high explosives (IHEs) is key for the design of new insensitive materials with improved response. We explore high temperature reaction kinetics and identify reaction mechanisms for the IHE LLM-105 through all-atom molecular dynamics performed at two levels of quantum chemical theory and with classical reactive potentials. Short timescale DFT-MD simulations are used to cross-validate density functional tight-binding (DFTB) predictions, which in turn are compared against multiple ReaxFF parametrizations. We characterize the time histories of local bonding environments to show that LLM-105 chemistry is highly similar to TATB, with some HMX-like aspects. High-throughput DFTB and ReaxFF simulations are coupled with the Hugoniostat technique to simulate shock loading and to characterize the Hugoniot curves for both unreacted LLM-105 and its products. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Approved for unlimited release LLNL-ABS-815962. |
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H71.00244: Anomalous compressibility in 1T' MoTe2 single crystal: High-pressure Raman and structural studies Bishnupada Ghosh, Pinku Saha, Goutam Dev Mukherjee A detailed high-pressure study is carried out on 1T' MoTe2 using X-ray diffraction (XRD) and Raman spectroscopy measurements up to about 30.5 GPa. High-pressure XRD measurements show no structural transition. All the lattice parameters exhibit anomalous changes in the pressure region 8.4 to 12.7 GPa. The compressibility of the sample is found to be reduced by almost four times above 12.7 GPa with respect to that below 8.4 GPa. The anomalies in the Raman mode corresponding to the out of plane vibrations of Mo atoms sitting in the unit cell surface indicate a strong electron-phonon coupling possibly mediated by differential strain inside the unit cell. The high-pressure resistivity measurement at room temperature shows a rapid decrease in resistivity with increasing pressure up to 8 GPa with respect to the variation at higher pressure. |
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H71.00245: Simulation of ion trajectories during Laser Ablative Mass Spectrometry of Energetic Materials. SASANK GUNDU, Prem Kiran Paturi, Ashoka Vudayagiri The high power laser incident on an Energetic Materials,EM creates temperatures of the order of few eV to tens of KeV and pressures of the order of MPa to GPa. The initial conditions of P,T are known to play crucial role in the decomposition pathway of EMs, which in turn are controlled by incident laser parameters. The laser ablative pressures and temperatures will vary the initial conditions of EMs and result in completely different pathways in contrast to the well-known thermal decomposition of EMs [1]. Study of the common gaseous by-products such as Carbon Dioxide, Water, Carbon Monoxide, Nitrogen Dioxide from the pulsed laser induced decomposition,LID of Energetic Materials,EM simulated using COMSOL-Multiphysics is presented. The laser induced pressure and temperature on the gas molecules were parameterized in terms of varying initial kinetic energy of oxides of C,H,N over the range of 0.5eV to 5eV. The evolution of various end products at the detector of a Quadrupole Mass Spectrometer, QMS is simulated. The stability zone and effect of initial velocities of the ions on the stable trajectory of ions were determined from the simulations. |
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H71.00246: Reduced order chemistry models for RDX decomposition using unsupervised and self-supervised learning techniques Michael Sakano, Edward Kober, Alejandro Strachan Detonation initiation is an important phenomenon in the field of high-energy materials, as it remains poorly understood even after decades of experimental and theoretical work. Key to developing this knowledgebase and predictive models are reduced order chemistry models capable of capturing the effects of pressure and temperature. Early efforts produced first principles gas-phase calculations schemes and more recently, work involving molecular dynamics (MD) to describe condense phase effects. The challenge is extracting reduced order models from all-atom MD simulations. To address this gap, we explore two techniques for dimensionality reduction to extract coarse grain models for a range of reactive MD simulations. We construct reduced order chemistry models for condensed-phase RDX from MD simulations at various temperatures and pressures. Using non-negative matrix factorization, we find that three components are enough to accurately describe the complex chemistry of RDX. A second chemistry model is developed using an autoencoder; the latent, encoded matrix results in slightly different concentration profiles. This results in differences in the chemical kinetics rate parameters between the two models. Approved for unlimited release LA-UR-20-29002. |
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H71.00247: Application of the New Alumina Travel Time Pressure Scale to Study the Elasticity of Materials at Simultaneous High Pressure and High Temperature Siheng Wang, Xintong Qi, Sibo Chen, Baosheng Li Recently, a new method has been developed for in-situ pressure (P) determination in multi-anvil apparatus within the framework of acoustoelasticity. The acoustic travel times of Al2O3 were calibrated against the NaCl pressure scale up to 15GPa, 1173K in conjunction with synchrotron X-radiation, thereby providing a convenient and reliable gauge for pressure determination at ambient and high temperatures (T). As indicated by recent experiments at room temperature, the pressures derived from this new method are in excellent agreement with those from the fix-point methods, and the resultant equations of state on several materials (e.g., coesite, tungsten, hafnium, etc.) revealed remarkable agreement with those from the previous compression studies under hydrostatic conditions. In this study, the new experimental capability has been extended to experiments at simultaneous high P-T and is illustrated by our recent ultrasonic measurements on body-centered-cubic-Fe90Ni10 up to 8GPa and 773K. The successful application of Al2O3 travel time pressure gauge to high T experiments is expected to open new opportunities for offline laboratory studies of solid and liquid materials under high P-T in multi-anvil apparatus. |
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H71.00248: LASER SCIENCE
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H71.00249: Evanescent Light Coupling Between Waveguides and Optical Microparticles with Whispering Gallery Resonances Hyunjun Park, Oleksiy V Svitelskiy Optical microparticles with spherical, cylindrical, or elliptical symmetry are known to possess Whispering Gallery Mode (WGM) resonances. Interactions of these microparticles with an evanescent light field of, for example, a tapered optical fiber, opens up a possibility for the resonant propelling of such microparticles with high selectivity by wavelength and by size. In order to optimize this sorting process, in the present work we develop a computational model that describes the evanescent light propagation along the tapered fiber and its coupling to a WGM resonator. This model is based on the commercial software package COMSOL. It is capable of predicting various experimental parameters. In particular, it allows to estimate the distribution of the evanescent field around the tapered optical fiber, to calculate WGM resonance spectra of light absorption and transmission by the resonator, and to determine the optimal distance between particle and waveguide. The high quality of the model is demonstrated by the excellent agreement between the measured and simulated WGM resonance spectra. |
(Author Not Attending)
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H71.00250: Hyperspectral Coherent Diffractive Imaging Spectroscopy of Phase and Oxidization State Co-existence Allan Johnson, Jordi Valls Conesa, Luciana Vidas, Daniel Perez-Salinas, Christian M Günther, Bastian Pfau, Kent A Hallman, Richard F Haglund, Stefan Eisebitt, Simon Wall Coherent diffractive imaging (CDI) has been proposed as a promising method to study light-induced transient phases in quantum materials which exhibit intrinsic nanoscale phase co-existence [1]. Identifying and characterizing material phases in the condensed phase implies going beyond imaging alone and requires full-spectrum information, particularly for phases which may not exist in equilibrium, but this capability has yet to be demonstrated with coherent imaging methods. We have extended CDI to a full spectro-microscopy technique and used it to acquire hyperspectral images of vanadium oxide thin films with nanoscale resolution [2]. Using the full spectral information we identify the co-existence of multiple oxidization states without a priori information. Heating the sample we induce the insulator-to-metal phase transition in the VO2 fraction of the sample, imaging the phase co-existence and recovering the full complex refractive index of all states present. Our results rule out the role of any intermediate phases in the VO2 transition, and pave the way for future time resolved studies of light induced transient phases. |
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H71.00251: Optimizing Light Coupling into Microresonators with Whispering Gallery Modes for Optical Sorting Techniques Benjamin Martin, Nathan J Jordan, Alexander S King, Oleksiy Vasily Svitelski, Kamil Ekinci, Sean Andersson Our goal is to develop an effective device to sort microparticles using Whispering Gallery Mode (WGM) resonances. The device is centered on a tapered optical fiber, immersed in a liquid suspension with microparticles of interest. The fiber is fed by laser light of a particular wavelength. As microparticles come in contact with the tapered section of the fiber, the particles whose resonance match the wavelength of the laser will be selectively moved by evanescent light along the taper into a special container. This method allows for sorting particles with unprecedented selectivity, with immediate applications in photonics, microbiology, biomedicine, and pharmaceuticals. In order to optimize this sorting method, we compare two different fiber-tapering techniques. The first one is chemical etching in hydrofluoric acid; the second technique is heating and pulling the fibers. Both methods allow for making tapers down to a diameter of 1-3 microns. The smaller diameters allow for higher efficiency of light coupling. However, due to their small size, they are more vulnerable to breaking. |
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H71.00252: Light by Design for Next-Generation Electron Beams Sources and X-ray Free Electron Lasers Sergio Carbajo Unifying laser and accelerator physics holds great promise for the development of future particle accelerators, light sources, and other scientific instruments due to increasingly synergistic advances at the cross-section between these two fields. Their combined action has recently ushered in advanced scientific facilities to study the ultrafast dynamics of matter at the atomic level. We will review state-of-the-art optical laser upconversion[1] and conditioning[2,3] technologies and methodologies for future electron beam sources, linear accelerators, and X-ray free-electron lasers, including adaptable generation and conditioning of electron beams at high repetition rates. |
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H71.00253: Towards Real-time Programmable Laser-based Photoinjector Shaping for LCLS-II and Beyond Jack Hirschman, Naoufal Layad, Randy Lemons, Federico Belli, Sergio Carbajo, Ryan N Coffee The next generation of high brightness X-ray free electron lasers (XFEL), such as SLAC’s LCLS-II, promises to address current challenges associated with systems with low X-ray cross-sections. A key component of XFELs is the photoinjector [1], which produces the electron beams (e-beams) whose phase-space determines the performance of the XFEL. Active e-beam manipulation techniques and diagnostics are required in order to fully capitalize on this new generation of XFELs. We examine a possible solution for adaptive e-beam shaping using a hardware-based machine learning implementation of real-time photoinjector laser manipulation. Our presentation will provide an overview of this project, the five-year goals, and the work both completed and currently underway, in particular simulations of the system and hardware design for the requisite real-time X-ray diagnostics. We anticipate this approach to not only enable active experimental control of X-ray pulse characteristics but also to increase the operational capacity of future e-beam sources and accelerator facilities. |
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H71.00254: 4D Light Bullets with Programmable Vector Field Distributions Randy Lemons, Wei Liu, Josef Frisch, Alan Fry, Joseph Robinson, Steve Smith, Sergio Carbajo
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H71.00255: Genetic Algorithm Reconstruction of Coherent Combination-Based Programmable Structured Light Randy Lemons, Sergio Carbajo
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H71.00256: Self-modulation oscillations and Q-switched mode-locking of Vortex Laser Formed by Coherent Superposition of Off-axis Traveling Waves Prof. Lin We generated diode pumped optical vortex laser with self-modulation oscillation and Q-switched mode-locked vortex lasers in the proposed azimuthal symmetry breaking ring resonator. In the laser resonator are placed an a-cut Nd:YVO4 crystal, a focusing lens of 10-cm-focal-length and a spiral phase plate (SPP) carrying a topological charge of positive one. Because the azimuthal symmetry is broken by the intra-cavity SPP, lights can only travel off-axis along a ring trajectory in either clockwise or counterclockwise manner. With sufficient pump, linearly polarized laser with a doughnut-shaped intensity profile and a positive unit topological charge was emitted. Without any intracavity modulating elements, vortex laser power spectrum contains a few harmonics of 82.5 kHz. The oscillations were identified as self-modulation oscillation. We also study the laser mode-locking in this vortex laser by inserting an acousto-optic modulator into the laser resonator and signature of laser mode-locking was observed within the Q-switched envelope. Notably the self-modulation oscillation and mode-locked vortex pulses were synchronized among the off-axis traveling-wave modes. |
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H71.00257: Direct observation of acoustic phonon oscillations in the Weyl semimetal TaAs using ultrafast x-ray diffraction Min-Cheol Lee, Nicholas Sirica, Samuel Teitelbaum, Alexei Maznev, Thomas Pezeril, Roxanne Tutchton, Viktor Krapivin, Gilberto de la Pena, Yijing Huang, Jiaojian Shi, Jian-Xin Zhu, Dmitry Yarotski, Xianggang Qiu, Keith Adam Nelson, Mariano Trigo, David A Reis, Rohit P Prasankumar In the Weyl semimetal TaAs, we investigated optically excited acoustic phonon oscillations using time-resolved X-ray diffraction. The unique surface orientation (112) of the TaAs crystal enabled the simultaneous observation of longitudinal and shear acoustic modes, whose dispersion closely matches our simulations. The long penetration depth and high temporal resolution of femtosecond X-ray pulses allow us to observe an asymmetric lineshape of the longitudinal mode, which is absent from the shear mode. We attribute this spectral asymmetry to a time-dependent frequency chirp resulting from the thermal diffusion of photoinduced carriers. Our study also highlights the benefit of using off-axis crystal orientations in topological materials to optically excite shear deformations, allowing one to transiently control crystal structures of these materials and potentially their topological properties. |
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H71.00258: ATOMIC, MOLECULAR, AND OPTICAL PHYSICS
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H71.00259: Boosting Light Emission from Single Hydrogen Phthalocyanine Molecules by Charging Vibhuti Rai, Lukas Gerhard, Qing Sun, Christof holzer, Taavi Repaen, Marjan Krstic, Liang Yang, Martin Wegener, Carsten Rockstuhl, Wulf Wulfhekel Recently, light emission from single molecules on insulating layers studied by scanning tunneling microscopy (STM) has made considerable progress. Many fundamental aspects of light emission, however, remain unclear for the future prospect of device applications. In this work, we used a home-build STM with high light-collection efficiency [1] to investigate light emission from individual Hydrogen-Phthalocyanine molecules thermally evaporated onto bi- and trilayers of NaCl on Au(111). By combining STM, full wave electrodynamics and quantum chemical calculations, we show that the light emission efficiency of an individual hydrogen-phthalocyanine molecule can be increased by a factor of ≈19 upon charging [2]. This boost can be explained by the development of a vertical dipole moment normal to the substrate, facilitating out-coupling of the local excitation to the far field. Since this effect is not related to the specific molecule, it provides a general pathway for enhancing the quantum efficiency of light emission from a molecular junction. |
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H71.00260: High-temperature phosphor thermometry with YAG: Dy and LED excitation Atul Regmi, Stephen W. Allison, Kathy Olenick, Firouzeh Sabri We aim to extend the temperature range of phosphor thermometry as a diagnostic tool for the protective properties of thin flexible ceramic strips of Yttrium Stabilized Zirconia (YSZ) and its uses. Previous investigations demonstrated adequate optical transmission properties of Manganese doped Magnesium Flurogermanate and Lanthanum Oxysulphide thermometry between 90 C and 700 C using 405 nm diode laser excitation and several different phosphors. Also, in an earlier study, multiple layers of ceramic ribbons were tested in the temperature range reported. Here, YAG: Dy was selected for extending the range of applications to a higher temperature, nearing 1200 C. To accomplish this the thermographic phosphor was coated in a thin uniform layer of the YSZ ceramic ribbon. Using direct 365 nm UV LED excitation and monitoring from 4I15/2 to 6H15/2 transition at 456 nm. Temperature-dependent luminescence was observed from ambient to 1200 C. The decay characteristics did not show a strong temperature dependence up to ~900 C. However, with temperatures exceeding 900 C, the decay time decreased as a function of temperature. To the best of our knowledge, this is the first published use of LED excitation of a thermographic phosphor past 1000 C. |
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H71.00261: Long-range additive and nonadditive interactions for the excited Li(2 2S)-Li(2 2P)-Li+(1 1S) system Pei-Gen Yan, Li-Yan Tang, Zong-Chao Yan, James Babb Using degenerate perturbation theory, the long-range interactions for a three-body hybrid atom-ion system composed of one ground S state Li atom, one excited P state Li atom and one ground S state Li+ ion are evaluated with highly accurate variationally-generated wave functions in Hylleraas coordinates. The detailed long-range potential curves are plotted for the equilateral triangle and for the linear congurations. We demonstrate that the nonadditive interactions that are induced by the degeneracy and enhanced by the induction effect in the three-body system play a signicant role and should be accounted for in constructing precise potential energy surfaces. We explore the competition for M = 0 quantum states between the attractive term C4 / r4 and repulsive term C6 / r6 when the internuclear distances r becomes smaller. |
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H71.00262: Generally Covariant Generalization of The Dirac Equation (a new pde) That Does Not Require Gauges Joel Maker Toward the end of his life Dirac tried to modify his equation so that it did not require infinities and a 1096gram/cm3 vacuum density to get the correct Lamb shift and gyromagnetic ratio. He said ”other people, I hope, will follow along such lines.“ Well, it is easy to fix this problem. Instead of linearizing a flat space Minkowski metric as Dirac did to get his Clifford algebra, leave it as a Schwarzschild metric with rH =2e^2/mec^2 instead of 2GM/c^2 in 1-rH/r=kooalso thereby maintaining a general covariance for the Dirac equation. Divide by ds^2 and define px=dx/ds and we then get using Dirac gammax=Gx: (Gxkxx^.5px+Gykyy^.5py+Gzkzz^.5pz+Gtktt^.5pt)2=kxxpx2+kyypy2+kzzpz2+kttpt2. Linearize like Dirac did: Gxkxx^.5px+Gykyy^.5py+Gzkzz^.5pz+Gtktt^.5pt. Plug in the operator formalism and we get a generally covariant pde (Gi(kii^.5)(dpsi/dxi)=(w/c)psi. The energy turns out to be E=1/k00 =1/(1-rH)1-rH/2r+(3/8)(rH/r)^2 +..=1-Vc+dV with normalization coefficient mc^2. So that integral[2,0,0*dV2,0,0dV]=V=Lamb shift. We get an equivalence principle for kij by assuming the only particle with nonzero rest mass is the electron (with the rest composites, DavidMaker.com) and that above splitting of rH comes from a cosmological and electron selfsimilar (fractal) universality of this new pde. |
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H71.00263: The Field’s Interaction and Atomic Model Mahmoud Yousif The Rutherford’s atom was rejected due to the perceived depletion of energy by electron when accelerated towards nucleus, hence the collapse of the atom; that was replaced by Bohr model; earlier, Ørsted discovered electric current produced Circular Magnetic Field (CMF), this later realized to be produced by charged particles (electrons and protons): this important characteristics never been incorporated into any theoretical model; while the recent derived field’s interaction formula, based on Faraday’s concept of attractive and repulsive characteristics of magnetic lines of force, make it possible to derived the magnetic force formula as due to mutual interaction of two CMF and CMF with magnetic field, in it (Fm=B1U B2e rme2 c), B1U is nucleus Spinning Magnetic Field (SMF), B2e is orbital electron’ CMF, rme is magnetic radius, c speed of light; this formula allowed for the atomic forces to be tackled based on the balance of both the electrostatic force (Fe) and Magnetic Force (Fm) with the Centripetal Force (Fc), the paper elaborate the continual energization of the electron within the natural orbit and when excited within the influence of the nucleus, and the mechanism and formulas for the radiated spectral lines; the paper seeks the truth in physics science. |
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H71.00264: Measurement of photoionization cross-sections from 6s5d 1D2 excited state of ytterbium at and above the first ionization threshold. Bilal Shafique, Raheel Ali, Sami ulHaq, Muhammad Rafique, Muhammad A Baig Experimental investigations of photoionization cross sections from the even-parity excited state 6s5d 1D2 of atomic ytterbium are reported. A heat pipe-cum-linear thermionic diode ion detector, working in space charge limited mode, has been used for generating the atomic vapors of Yb. An Nd:YAG pumped narrow bandwidth (~ 0.2 cm-1) Hanna-type dye laser, charged with LDS-698 dye and tuned at 722.6 nm, was used to excite electrons via two-photon transition 6s2 1S0 → 6s5d 1D2. The excited state population is then promoted to the ionization threshold at 439.2 nm and above the threshold at 355 nm and 266 nm wavelengths. To measure the photoionization cross section from the excited state, the saturation technique has been employed, in which the intensity of the exciting laser (722.6 nm) is kept fixed while that of the ionizing laser is varied using neutral density filters. The photo-ion signal from the excited state at and above the threshold region was recorded as a function of ionizing laser intensity, which yield the cross section in the range 230± 13 Mb to 32.6 ±1.2 Mb. To the best of our knowledge, measurement of photoionization cross sections from the 6s5d 1D2 excited state of atomic ytterbium is the first time reported. |
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H71.00265: Topologically quantized current in quasiperiodic Thouless pumps Pasquale Marra, Muneto Nitta Thouless pumps are topologically nontrivial states of matter with quantized charge transport, which are analogous to the quantum Hall state and can be realized by ultracold atomic gases in optical lattices. However, contrarily to the exact and extremely precise quantization of the Hall conductance, the pumped charge is quantized only when the pumping time is a multiple of a characteristic time scale, i.e., the pumping cycle duration. Here we consider the quasiperiodic regime realized via the superposition of two distinct optical lattices with incommensurate wavelengths. We show that in this case the Bloch bands and the Berry curvature become flat, the pumped charge becomes linear in time, while the current becomes steady, topologically quantized, and proportional to the Chern number, independently from the pumping time[1]. The current quantization is exact up to exponentially small corrections. This has to be contrasted with the case of the non-quasiperiodic regime, where the current is not constant, and the pumped charge is quantized only at integer multiples of the pumping cycle. |
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H71.00266: Relativistic strong-field ionization dynamics of hydrogenlike ions within and beyond the dipole approximation Dmitry A. Telnov, Shih-I Chu We perform a theoretical and computational study of the hydrogen atom and hydrogenlike ions Ne9+ and Ar17+ subject to strong pulses of linearly-polarized electromagnetic fields. To solve the problem, we apply the generalized pseudospectral method for the Dirac equation in spherical coordinates and suggest a transformation of the Hamiltonian that removes the spurious eigenstates. The ionization probabilities are calculated for several peak field strengths both within and beyond the dipole approximation. We compare the ionization probabilities for these hydrogenlike systems subject to the external fields with the appropriately scaled parameters, so the nonrelativistic treatment in the dipole approximation returns identical results for all three targets. We identify the field strength regions where the relativistic and nondipole effects become important. To assess the applicability of the dipole approximation, we calculate the Lorentz deflection parameter proposed previously to estimate the nondipole effects due to the influence of the magnetic component of the external electromagnetic field. Based on our present results, we find that the dipole approximation works well if this parameter is of the order of 10-3 or less. |
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H71.00267: Dynamics of enhanced and suppressed high-order harmonic generation of He atom by intense frequency-comb laser fields Chang-Tong Liang, Peng-Cheng Li, Shih-I Chu <font _mstmutation="1">We present an ab initio nonperturbative investigation of enhanced and suppressed high-order harmonic generation (HHG) of He atom driven by the intense frequency-comb laser fields. The HHG is calculated by solving three-dimensional time-dependent Schrödinger equation by means of the time-dependent generalized pseudospectral method. The results show that each harmonic from the first harmonic all the way to the cutoff has a nested comb structure, and the frequency comb structures show immense enhancement and suppression by tuning the number of short laser pulses. The underlying physical mechanism of enhancing and suppressing HHG is illustrated by the interference effect of the HHG spectra originating from each short laser pulse.</font> |
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H71.00268: Selection rule for topological amplifiers in Bogoliubov de Gennes systems Hong Ling, ben kain Dynamical instability is an inherent feature of a bosonic system described by the Bogoliubov de Geenes (BdG) Hamiltonian. It causes the BdG system to collapse and therefore should be avoided. Recently, there emerged proposals for harnessing this instability for the benefit of creating a topological amplifier characterized with stable bulk bands but unstable edge modes that are populated at an exponentially fast rate. We formulate a theorem for determining the stability of a state with energy sufficiently far from zero, in terms of an unconventional "commutator" between the number conserving part and nonconserving part of the BdG Hamiltonian. We apply the theorem to a generalization of a model by Galilo et al. [Phys. Rev. Lett, 115, 245302(2015)] for creating a topological amplifier in an interacting spin-1 atom system in a honeycomb lattice through a quench process. We use it to illustrate how the vanishing of this \commutator” selects the symmetries that a system has to have so that its bulk states are stable against (weak) pairing interactions. We find that as long as the time reversal symmetry is preserved, our system is capable of acting like a topological atom laser even in the presence of the onsite staggered potential which breaks the inversion symmetry. |
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H71.00269: Dissipation-induced current rectification in nonequilibrium steady states of open many-body systems Kazuki Yamamoto, Yuto Ashida, Norio Kawakami Nonreciprocal phenomena have been a long-standing problem in condensed matter physics and nonequilibrium statistical mechanics. In open quantum systems, one common way to introduce rectification is to couple a system with two different baths at boundaries and use temperature gradients. Such studies focus on inhomogeneous setups by boundary driving. In contrast, theory for rectification induced by homogeneous dissipation of nonequilibrium baths has not been established yet. |
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H71.00270: High-order Harmonic Spectra in different gauges can disagree when there is confinement Turker Topcu, Erdi Ata Bleda, Zikri Altun We test the common wisdom that the high-order harmonic generation (HHG) spectra agree well in all three length, velocity, and acceleration gauges obtained from a typical TDSE simulation when the system is in the weak-field regime. We show that the spectra in these gauges start to disagree significantly when state mixing is introduced without changing the dynamical regime. We demonstrate this by solving the time-dependent Schrödinger's equation (TDSE) and compare spectra in different gauges in 2 different situations: when (1) the atom is free of confinement, and (2) the atom is confined inside a C60 shell. When the atom is initially prepared in the ground state, size of which is smaller than the C60 radius, all three gauges agree very well regardless of whether the atom is confined. In the 3s excited state, however, a perfect agreement is only achieved between different gauges when the atom is free. Introducing confinement, in this case, results in mixing into the nearby n=4 manifold which results in significant disagreement between gauges. In all our calculations, we scale the laser intensity and wavelength such that the Keldysh parameter remains the same, which keeps our system in the same dynamical regime across different situations we investigate. |
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H71.00271: Quantum Many-Body Scars in Optical Lattices Hongzheng Zhao, Joseph Vovrosh, Florian Mintert, Johannes Knolle The concept of quantum many-body scars has recently been put forward as a route to describe weak ergodicity breaking and violation of the eigenstate thermalization hypothesis. We propose a simple setup to generate quantum many-body scars in a doubly modulated Bose-Hubbard system which can be readily implemented in cold atomic gases. The dynamics are shown to be governed by kinetic constraints which appear via density-assisted tunneling in a high-frequency expansion. We find the optimal driving parameters for the kinetically constrained hopping which leads to small isolated subspaces of scared eigenstates. The experimental signatures and the transition to fully thermalizing behavior as a function of driving frequency are analyzed. |
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H71.00272: Time Dynamics and Green’s Functions of a Driven-Dissipative Bose-Hubbard Dimer Matteo Seclì, Massimo Capone, Marco Schiro The fast advances in the QED quantum simulators1,2,3,4 call for the development of theoretical tools to study out of equilibrium nonlinear cavities. In this work5 we report a numerical study of the building block of these systems, a dimer made by two driven-dissipative coupled cavities, provided with a Kerr nonlinearity. Despite its simplicity, this is a completely non-trivial system which sheds light on larger lattices. While under a semiclassical analysis the system experiences a phase transition from a localized to a delocalized regime even in the open case, the numerically exact solution of the quantum system shows no sharp transition. We also show that while the open nature of the system does not allow to gain insights on the Hamiltonian from a long-time analysis of quantum mechanical observables unless an effective loss imbalance is realized, a rich information about the quantum spectra is encoded in the single-particle Green’s function. |
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H71.00273: Coherent Perfect Absorption in Cavity Quantum Electrodynamics Pawan Khatiwada, Zibo Wang, Dan Wang, Imran Mirza Coherent Perfect Absorption (CPA) is a phenomenon in which the light incident on a lossy medium is completely absorbed by destructive interference among all scattering amplitudes. First introduced by Douglas Stone group at Yale in 2010 as an anti-laser [1], it was demonstrated with ~99.4% absorption in 2011 [2]. It has found applications in photodetection, solar cells, quantum information storage, etc. [3]. In this work, we discuss how the CPA can be realized in cavity quantum electrodynamics. Our system consists of two laser beams shined on the mirrors of a bidirectional single-mode optical cavity with two-level atoms trapped inside. We derive the quantum Langevin equations and analyze the steady-state solutions to find the conditions to accomplish CPA. As an extension of this work, we consider two interacting two-level atoms trapped inside the same type of optical cavity. We particularly focus on how interatomic interactions can impact the CPA under the weak-excitation limit. |
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H71.00274: Direct loading of optical traps using hollow-core photonic crystal fibers Jakob Rieser, Stefan Lindner, Maxime Debiossac, Markus Aspelmeyer, Nikolai Kiesel Optical levitation of nano-particles provides novel approaches to cutting-edge sensors and tests of quantum physics at unprecedented mass scales. Today, experiments already operate in a regime (~ 1E-8 mBar) where decoherence from photonic recoil due to the optical trap starts to dominate over gas scattering [1] and where the quantization of the energy spectrum becomes relevant [2,3]. |
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H71.00275: Optical storage and retrieval of arbitrary pulse shapes Billie DeLuca, Dr. Anil Patnaik As quantum information science advances, the storage and accurate retrieval of quantum states as light pulses will be vital for viable quantum ‘memory'. With the pursuit of quantum storage in mind, in this paper we expand the analysis done previously on storing Gaussian light pulses to undefined pulse shapes and derive a generalized expression for the retrieved light pulse from electromagnetically induced transparency (EIT) storage in a three-level Λ system. Starting from the coupled differential equations that govern the retrieval of the stored pulse, we derive a formula using parameters of the control pulses and the atomic system that can be used with any arbitrary pulse shape to be stored. We also examine the role of a modified reading pulse for increasing the fidelity of the retrieval process. We compare the results of our formula to explicitly calculated results for the Gaussian pulse, then calculate results using our formula for other probe pulse shapes, including double-Gaussian and super Gaussian pulses. The study will be extended to further explore storage and retrieval of quantum information. |
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H71.00276: Quantum fluctuations on top of the Gutzwiller approximation in the Bose-Hubbard model: static and dynamical correlations Fabio Caleffi, Alessio Recati, Iacopo Carusotto, Massimo Capone, Ines de Vega, Chiara Menotti We develop a quantum many-body theory of the Bose-Hubbard (BH) model based on an improved Gutzwiller scheme. Our quantum theory is a generalization of the Bogoliubov theory of weakly-interacting gases and have common features with slave boson techniques. |
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H71.00277: Quantum Adiabatic Doping with Optical Lattice Jue Nan Quantum simulations of Fermi-Hubbard models have been attracting considerable efforts in the optical lattice research, with the ultracold anti-ferromagnetic atomic phase reached at half filling in recent years. An unresolved issue is to dope the system while maintaining the low thermal entropy. We propose to achieve the low temperature phase of doped FermiHubbard model via converting two lattices with different spacing period. We firstly demonstrate the feasibility of this proposal using a generic irrational filling factor and simulate the adiabatic evolution of free fermions in one- and two- dimensional lattice. The incommmensurate lattice induces localization problem which prevents the adiabatic preparation. We introduce the interaction to solve the localization slowing down. The DMRG calculation show that the preparation efficiency can be strongly enhanced. We extend this proposal to a wide range of filling factors and find that the localization also exists for finite-size system with rational filling. The efficiency of the hole doping is generally much higher than the particle doping because the large tunneling reduces the localization. We also consider starting from Mott insulator state instead of band insulator which further improves the efficiency for some filling. |
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H71.00278: On Universal Mass, Velocity and Gravity Triplet Zhi an Luan In 2019, I cast the Generalized Newton’s Laws that the tensor product of m-v is controlled by a monodromy gravitational constant family: |
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H71.00279: Enhancing spin-phonon and spin-spin interactions utilizing the linear resources in a hybrid quantum system Yuan Zhou, Peng Bo Li, Wei Bo Gao, Franco Nori Improving the spin-phonon and spin-spin couplings in hybrid quantum systems remains a crucial challenge. Here, we propose an experimentally feasible and simple method for exponentially enhancing the spin-phonon and the spin-spin interactions in a hybrid spin-mechanical setup, using only linear resources. Through modulating the spring constant of the cantilever with a time-dependent pump, we can acquire a tunable and nonlinear drive to the mechanical mode, thus amplifying the mechanical zero-point fluctuations and directly enhancing the spin-phonon coupling. This method allows the spin-mechanical system to be driven from the weak-coupling regime to the strong-coupling regime, and even the ultra-strong coupling regime. This method also gives rise to a large enhancement of the phonon-mediated spin-spin interactions between distant solid-state spins, typically two orders of magnitude larger than that without modulation. |
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H71.00280: A UV Laser System for Spectroscopy of AlCl at 261nm Chen Wang, John Daniel, Taylor Lewis, Alexander Teplukhin, Brian Kendrick, Chris Bardeen, Shan-Wen Tsai, Boerge Hemmerling Ultra-cold dipolar molecules offer platforms for precision measurements of fundamental constants, quantum computation, study of ultracold chemistry and other novel physics. Aluminum mono-chloride (AlCl) has been predicted as a promising candidate for laser cooling and trapping. We use a frequency-tripled CW Titanium-Sapphire laser to do spectroscopy of AlCl generated via laser ablation of AlCl3 in a cryogenic helium buffer-gas beam source. The spectroscopy light is produced by first frequency-doubling 784nm to 392nm. The 392nm light is then combined with the fundamental in a sum-frequency process to create light at 261nm. Here,we discuss details of our molecular beam source and our laser system for generating UV light and we present our spectroscopy results for the X1Σ+→A1Π transition in AlCl. |
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H71.00281: Stationary optomechanical entanglement between a mechanical oscillator and its measurement apparatus Corentin Gut, Klemens Winkler, Jason Hoelscher-Obermaier, Sebastian Hofer, Ramon Moghadas Nia, Nathan Walk, Adrian Steffens, Jens Eisert, Witlef Wieczorek, Joshua A Slater, Markus Aspelmeyer, Klemens Hammerer We provide an argument to infer stationary entanglement between light and a mechanical oscillator based on continuous measurement of light only. We propose an experimentally realizable scheme involving an optomechanical cavity driven by a resonant, continuous-wave field operating in the non-sideband-resolved regime. This corresponds to the conventional configuration of an optomechanical position or force sensor. We show analytically that entanglement between the mechanical oscillator and the output field of the optomechanical cavity can be inferred from the measurement of squeezing in (generalized) Einstein-Podolski-Rosen quadratures of suitable temporal modes of the stationary light field. Squeezing can reach levels of up to 50% of noise reduction below shot noise in the limit of large quantum cooperativity. Remarkably, entanglement persists even in the opposite limit of small cooperativity. Viewing the optomechanical device as a position sensor, entanglement between mechanics and light is an instance of object-apparatus entanglement predicted by quantum measurement theory. |
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H71.00282: Interacting ultracold fermions in one dimension Danyel Cavazos-Cavazos, Ruwan Senaratne, Ya-Ting Chang, Randall G Hulet Cold atoms provide a pristine and tunable platform for studying quantum gases in reduced dimensions. We report on our experimental studies of interacting fermions in quasi-1D, both in two-spin and single-spin systems, realized using combinations of the hyperfine sublevels of 6Li. In the two-spin case, we measure the low-energy collective excitations in the Tomonaga-Luttinger liquid regime, as a function of strong, repulsive interactions. We separately excite charge and spin modes via two-photon Bragg processes, and measure the dynamic structure factor for each mode at different interaction strengths, tuned via an s-wave Feshbach resonance. In the single-spin case, we observe the rate of collisional loss due to molecule formation near a p-wave Feshbach resonance [1]. Our results suggest a suppression of this loss process very close to the resonance for strong transverse confinement, as predicted due to the stretching of the molecular wavefunction in quasi-1D [2]. |
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H71.00283: Photoassociative Spectroscopy of 87Sr Joshua Hill, William Huie, Priyansh Lunia, Joseph D Whalen, Soumya K Kanungo, Yi Lu, F Barry Dunning, Thomas Charles Killian We demonstrate photoassociation (PA) of ultracold fermionic 87Sr atoms via the dipole-allowed atomic transition in Strontium (Sr) near 461nm. The binding energies of a series of molecular states on the 5s2 (1S0) + 5s5p (1P1 )molecular potential are fit with the semiclassical LeRoy-Bernstein model, and PA resonance strengths are compared to predictions based on the known 1S0 + 1S0 ground state potential. Similar measurements and analysis were performed for the bosonic isotopes 84Sr and 86Sr, allowing a combined analysis of the long-range portion of the excited-state potential and determination of the 5s5p 1P1 atomic state lifetime. The results enable prediction of PA rates across a wide range of experimental conditions. |
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H71.00284: Molecular thermoelectric devices Oliver Schmuck, Davide Beretta, Ksenia Reznikova, Ross Davidson, Oliver Braun, Mickael Perrin, Martin R. Bryce, Marcel Mayor, Michel Calame Molecular devices could offer new paths to pursue efficient thermal-to-electrical energy conversion at room temperature by controlling the alignment of the devices' energy levels directly at the nanoscale and/or by exploiting quantum interference effects.1 |
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H71.00285: Planck Calculation of both Proton and Electron Mass Understanding Relationship as (re/a0)3/4, also (α2)3/4, ‘Mass’ Scaling Method of 1,602:1 further Applied with the Pauli-Hemisphere Pair Physical Model Generating Settling at 8/7+Anamolous Moment, s Arno Vigen I examine the ‘mass’ concept as the relative excess direct nucleostatic (“N-S”) (strong nuclear) field applied to electron-nucleus-electron interactions a) as (re/a0)3/4, 1,604.2; b) plus the physical logic of that Pauli-hemisphere using which scales times 8/7, so 1,836: |
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H71.00286: Quantum optics with noble-gas spins Roy Shaham, Or Katz, Ofer Firstenberg Noble-gas nuclear spins are extremely isolated from the environment and can maintain spin coherence for hours. Unfortunately, these spins are not accessible to light in the optical domain. Therefore, as opposed to optically-accessible alkali-metal spins employed in quantum optics and metrology, the (potential) quantum qualities of noble-gas spins have been beyond reach and largely ignored. We show that thermal spin-exchange collisions between noble-gas and alkali-metal spins form a quantum interface between them. Despite their stochastic nature, these weak collisions accumulate to a deterministic, efficient, and controllable coupling between the collective spins of the two ensembles. The interface paves the way to employing the long coherence time of noble-gas spin in the quantum domain. We present a quantum treatment of the stochastic collisional process and analyze the prospects for realizing non-classical states and quantum memories with hour-long lifetimes. In experiments, we realize the strong coupling of potassium to helium-3 spins and witness their periodic exchange of spin coherence. We then introduce light fields and demonstrate the efficient optical interface to helium-3. We discuss the prospect for generating long-lived entanglement between distant noble-gas ensembles. |
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H71.00287: Buffer gas cooling and optical cycling of AlF molecules Simon Hofsaess, Maximilian Josef Doppelbauer, Sebastian Kray, Boris Sartakov, Jesús Pérez-Ríos, Gerard Meijer, Stefan Truppe We have recently identified the aluminum monofluoride (AlF) molecule as an excellent candidate for laser cooling and trapping at high densities, measured the detailed energy level structure of the electronic states relevant for these processes and analyzed possible loss channels from the cycling transition. |
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H71.00288: Atom interferometry with thousand-fold increase in dynamic range Chen Avinadav, Dimitry Yankelev, Nir Davidson, Ofer Firstenberg Atom interferometry offers extremely high sensitivity in measuring acceleration, gravitational fields and their gradients, and rotations. It is a promising technology for applications such as gravity surveys and navigation systems, which require operation in mobile and potentially unstable environments, measuring rapidly-changing, unknown signals. These challenges motivate development of new techniques to improve the sensitivity [PRA 100, 023617 (2019)], scale factor stability [PRA 102, 013326 (2020)] and dynamic range [PRApplied 13, 054053 (2020)] of atom interferometers under such conditions. |
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H71.00289: Statistical Properties of the Non-Hermitian SSH Model and Symmetry Inheritance owing to Real Spectra Ken Mochizuki, Naomichi Hatano, Joshua Feinberg, Hideaki Obuse We explore statistical properties of eigenvalues in Su-Schrieffer-Heeger model with imaginary on site potentials (non-Hermitian SSH model), whose hopping terms are randomly distributed spatially. We prove that, originating from a structure of the Hamiltonian, eigenvalues can be entirely real without Parity-Time symmetry [1] in a certain parameter region [2]. Also, we clarify that level statistics obey that of Gaussian orthogonal ensemble (GOE) when the Hamiltonian has entirely real spectra [2]. To this end, we show a general fact that a non-Hermitian Hamiltonian whose eigenvalues are real is mapped to a Hermitian Hamiltonian which shares the same symmetries with the original Hamiltonian [2]. When imaginary eigenvalues exist, we show that the density of states (DOS) becomes zero at the origin and diverges along the imaginary axis. We reveal that the divergence of DOS originates from Dyson singularity in chiral symmetric 1D Hermitian systems [2]. |
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H71.00290: Interplay of quantization and chaotic behaviour in ring-coupled condensates Damian Wozniak, Johann Kroha, Anna Posazhennikova We study large rings of weakly-coupled Bose-Einstein condensates, analysing in detail their dynamics and its dependence on the system size. Since we are interested in circulating currents and their quantisation, we consider initial conditions which result in potential maximisation of such current: equal site occupation and equal phase differences between neighbouring sites. Within the Gross-Pitaevskii approximation, we show that the current is quantised (exhibits sharp delta peaks) if the phase difference takes specific discrete values in the interval (π/2, 3π/2). The peaks, however, gradually average out to zero with increasing interaction due to chaos inherent to the system of many condensates. Eventually, the quantisation ceases to occur for a macroscopic number of sites, and the circular current manifests sinusoidal behaviour readily derived from the noninteracting limit. Marking the transition to the continuous limit. |
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H71.00291: Cavity-enhanced Raman scattering for in situ characterization of solid-state microcavities Sigurd Flagan, Daniel Riedel, Brendan Shields, Viktoria Yurgens, Tomasz Jackubczyk, Patrick Maletinsky, Richard J. Warburton The nitrogen vacancy centre (NV) in diamond constitutes a promising node in a quantum network owing to its highly coherent, optically addressable electron spin. However, scalability to more than a few network nodes is limited by the modest entanglement rates. One key issue is the poor extraction efficiency of coherent photons out of the host material. This issue can be addressed by coupling single NV centres to a resonant cavity, greatly enhance the photon flux owing to the Purcell effect [1]. |
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H71.00292: Numerical evidence for many-body localization in two and three-dimensions Eli Chertkov, Benjamin Villalonga, Bryan Clark Typically, quantum systems obey the laws of statistical mechanics and reach thermal equilibrium with their environment. However, many-body localization (MBL), a phenomenon that occurs in the presence of strong disorder and interactions, can give rise to quasi-local conserved quantities known as l-bits that prevent thermalization. While MBL has been shown to exist in 1D, a difficult open question has been to determine to what extent MBL exists in higher spatial dimension. In this talk, we present an algorithm [1] for finding approximate l-bits that we use to probe MBL physics in the disordered Heisenberg model in one, two, and three spatial dimensions and the hard-core Bose-Hubbard model in two dimensions. In all models studied, we find numerical signatures of a thermal-MBL transition and observe agreement with past observations of transitions in the 1D Heisenberg model and 2D hard-core Bose-Hubbard model. We make the first numerical observation of a transition to MBL physics in three dimensions. |
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H71.00293: The fate of the false vacuum: Finite temperature, entropy and topological
phase in quantum simulations of the early universe Peter Drummond, King Lun Ng, Bogdan Opanchuk, Margaret Reid, Manushan Thenabadu Despite being at the heart of the theory of the “Big Bang”, the quantum field theory prediction of false vacuum tunneling has not been tested. We give a numerical feasibility study of a table-top BEC quantum simulator proposal for this effect under realistic conditions. We report the observation of false vacuum tunneling in computer simulations, and the formation of multiple bubble ’universes’ with distinct topological properties. The tunneling gives a transition of the relative phase of coupled Bose fields from a metastable to a stable ’vacuum’. We include the finite temperature effects of a laboratory experiment and also analyze modulational instabilities in Floquet space. Our numerical model uses an approximate truncated Wigner (tW) method. We analyze a nonlocal observable called the topological phase entropy (TPE). A cooperative effect occurs, in which the true vacua bubbles representing distinct universes each have one or the other of two distinct topologies. The TPE initially increases with time, reaching a peak as multiple universes are formed, and then decreases with time to the phase-ordered vacuum state. This gives a model for the formation of universes with one of two distinct phases, which is a possible solution to the problem of particle-antiparticle asymmetry. |
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H71.00294: Prospects of Forming High-Spin Polar Molecules from Ultracold Atoms Matthew Frye, Jeremy Hutson We have investigated Feshbach resonances in collisions of high-spin atoms such as Er and Dy with closed-shell atoms such as Sr and Yb, using coupled-channel scattering and bound-state calculations. We consider both low-anisotropy and high-anisotropy limits. In both regimes we find many resonances with a wide variety of widths. The wider resonances are suitable for tuning interatomic interactions, while some of the narrower resonances are highly suitable for magnetoassociation to form high-spin molecules. These molecules might be transferred to short-range states, where they would have large magnetic moments and electric dipole moments that can be induced with very low electric fields. The results offer the opportunity to study mixed quantum gases where one species is dipolar and the other is not, and open up important prospects for a new field of ultracold high-spin polar molecules. |
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H71.00295: Universal metric for plasmonicity of excitations at the nanoscale Luca Bursi, Runmin Zhang, Kyle D. Chapkin, N J Halas, Peter Jan Arne Nordlander A promising trend in plasmonics involves shrinking the size of plasmon-supporting structures down to a few nanometers, thus enabling control over light−matter interaction at extreme-subwavelength scales. In this limit, quantum mechanical effects, such as nonlocal screening and size quantization, strongly affect the plasmonic response, rendering it substantially different from classical predictions. For very small clusters and molecules, collective plasmonic modes are hard to distinguish from other excitations, such as single-electrons ones. Using rigorous quantum mechanical computational techniques for a wide variety of physical systems, we describe how the plasmonic character of a nanostructure’s optical resonance can be quantified. We define a universal metric, the generalized plasmonicity index (GPI), which can be straightforwardly implemented in any computational electronic-structure or classical electromagnetic approach to discriminate plasmons from single-particle excitations and photonic modes [ACS Nano, 11, 7321 (2017); PNAS, 115, 9134 (2018); JPCC, 124, 20450 (2020)]. The GPI metric deepens our fundamental understanding of what is a plasmon down to the molecular limit of plasmon-supporting nanostructures and provides a rigorous foundation for molecular plasmonics. |
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H71.00296: Nonlinear Ionization Dynamics of a Laser Plasma Amplifier Michael Zuerch, Frederik Tuitje, Pablo Martinez Gil, Tobias Helk, Julien Gautier, Fabien Tissandier, Jean philipe Goddet, Alexander Guggenmos, Ulf Kleineberg, Stephane Sebban, Eduardo Oliva, Christian Spielmann From fusion dynamics in stars to novel light sources, hot dense plasmas are of importance for an array of physical phenomena. An insight of highly-ionized matter is crucial for understanding and controlling the generating processes. High-density plasmas are turbulent and opaque for radiation below the plasma frequency and allowing only a near-surface insight into ionization processes with visible light. Here, the output of a high harmonic seeded laser-plasma amplifier using eight-fold ionized krypton as gain medium operating at 32.8 nm wavelength is ptychographically imaged. A complex wavefront is observed in the extreme ultraviolet beam with high resolution. Ab initio spatio-temporal Maxwell-Bloch simulations show excellent agreement with the experimental observation revealing an overionization of krypton in the plasma channel due to nonlinear laser-plasma interactions. This constitutes the first experimental observation of the laser ion abundance reshaping the laser plasma amplifier. This finding has direct implications for upscaling plasma-based XUV and X-ray sources. Moreover, the presented approach shows the possibility to directly model light-plasma interactions in extreme conditions, such as present in early times of the universe, with direct experimental verification. |
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H71.00297: SEMICONDUCTORS, INSULATORS, AND DIELECTRICS
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(Author Not Attending)
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H71.00298: Structural, morphological, electrical and ferroelectric properties of lead free Ba0.985Sr0.015Zr0.10Ti0.90O3 ceramics Bablu Chandra Das, Farhad Alam, M. A. Matin, A. K. M. Akther Hossain The strontium and zirconium co-doped barium titanate compound have been chosen for analysis to explore Ba0.985Sr0.015Zr0.10Ti0.90O3 (BSZT) ceramic for energy storage applications. The selected compound was prepared using the standard solid state reaction technique and sintered at various sintering temperatures, Ts, 1200, 1250 and 1300°C. Rietveld refinement was used on the X-ray diffraction pattern to confirm the crystal structure of the BSZT samples and each sample indicates the tetragonal phase with the P4mm space group. Morphological analysis of the BSZT samples showed that higher Ts can attain a dense microstructure. Temperature and frequency dependence dielectric properties were studied. The relationship between the microstructural-properties (i.e. grain and grain boundary) and the relaxation process in BSZT was studied with detailed explanation of both the complex impedance and the modulus spectroscopy. A non-Debye type relaxation process was observed in BSZT. The ferroelectric behaviors of the sample were explored by recording the polarization versus electric field hysteresis loops at room temperature. |
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H71.00299: Electrical control of Rashba effect in a soft-paraelectric system Fan Yang, Turan Birol Ferroelectric Rashba semiconductors (FERSC) are promising materials candidates for spintronic applications. Their intrinsic, electrically-switchable ferroelectric polarizations enable electrical manipulation of spin currents through the Rashba spin-orbit coupling effect, which emerges in crystals with net electrostatic dipoles. However, the condition of ferroelectricity is very strict and limits the choices of materials significantly. In this study, we expand the search range of candidate semiconductors with electrically-controllable Rashba effect to include soft-paraelectric materials (i.e. paraelectric materials with large dielectric susceptibility), and focus on an wide-gap, incipient ferroelectric perovskite system, potassium tantalate KTaO3. By using a combined first-principles and group theoretical method, we show that in bulk KTaO3, the Rashba effect strengths and spin patterns of the spin-split bands are controllable through changing the electrostatic polarization magnitudes and directions. |
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H71.00300: Identifying Pb-free perovskites for solar cells by machine learning Suzune Omori, Hinako Hatanaka, Masanori Kaneko, Koichi Yamashita, Azusa Muraoka Hybrid halide perovskites are one of the new-age solar cells that are expected to solve the world's energy problems. In particular, lead-based halogen compounds with Pb2+ at the B-site, which have been most widely studied in photovoltaic applications. These materials can be easily produced at low cost, but they have drawbacks such as chemical instability and toxicity. Nakajima et al. search for novel materials for lead-free perovskite solar cells using the computational screening technique. In this study, we attempt to explore the candidate compounds of perovskite materials suitable for solar cells using statistics and multiple regression analysis, building predictive models and machine learning among these new material candidates. |
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H71.00301: Theory of hot carriers and carrier heating in a semiconductor under continuous illumination Subhajit Sarkar, Ieng-Wai Un, Yonatan Sivan, Yonatan Dubi The dynamics of the optically generated hot carriers in semiconductors are critically important to estimate the performance of electronic and optoelectronic devices. The interplay of optically generated carriers, their thermalization, and recombination leads to the formation of non-equilibrium distributions of hot carriers, and heating of carriers and phonons. Surprisingly, a theoretical framework, incorporating the non-equilibrium nature of the carriers and the carrier heating effect, is lacking to date. Here we present a semi-quantum coupled Boltzmann-heat equation formalism for calculating the non-equilibrium steady-state electron and hole distributions and temperatures. The formalism correctly accounts for energy and particle number conservation required for a physically-consistent solution of the Boltzmann equations. We show how the illumination energy splits between the different energy dissipation channels, and find a non-linear dependence of the electron and hole temperatures on illumination intensity, originating from the interplay between carrier-carrier interactions, carrier-phonon dissipation, and carrier recombination. These results are the first step towards a full estimation of hot-carrier generation on efficiency in solar cells and other optoelectronic devices. |
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H71.00302: A minimal model for the calculation of surface charges in GaAs/AlGaAs heterostructures Eleni Chatzikyriakou, Antonio LACERDA SANTOS NETO, Xavier Waintal We derive an analytical model to calculate charges accumulated at the surface of GaAs in a doped GaAs/AlGaAs heterostructure that is based on the electrostatics of the structure when biased under different voltages at its surface. We compare our results to self-consistent Poisson-Schrödinger calculations, performed using an in-house 1D solver. This model allows for the calculation of doping densities and charges accumulated in the 2DEG, even in cases where they are not directly measurable using experimental means. Our model reveals that the contribution of the spread of charges away from the interface has a more pronounced effect in shifting the voltage required to form the 2DEG at the surface of GaAs than the occupancy of the subbands. |
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H71.00303: Resonant Ultrasound Spectroscopy of KTa1-xNbxO3 and K1-xLixTaO3 Ferroelectric Relaxor Crystals Matthew Yoder, Nathan P Quattrochi, Emily M Gima, Oleksiy V Svitelskiy, Grace Jean Yong, Lynn A Boatner Resonance Ultrasound Spectroscopy (RUS) is a fast and nondestructive method to characterize elastic properties of materials. In this method the investigated sample is almost freely suspended between the excitation and receiving transducers. Scanning the excitation frequency, one can record a resonance spectrum of the sample. Further mathematical modelling allows to determine full set of elastic constants of the material investigated. KTa1-xNbxO3 and K1-xLixTaO3 relaxor ferroelectrics, due to the relative simplicity of their structure, represent a good test bed for modeling more complicated cases of lead relaxors. These materials are finding applications in the devices of adaptive optics. We apply the method of RUS to determine all independent elements of the elastic stiffness tensor for several crystals of KTa1-xNbxO3 and K1-xLixTaO3. To ensure convergence to the correct numbers, some of the values were cross-checked by ultrasound pulse-echo probing. |
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H71.00304: Exploring Solute Distribution and Clustering in GaAsBi and GaAsNBi Alloys Using Local- Electrode Atom Probe Tomography Jared Mitchell, Christian Greenhill, Tao-Yu Huang, Kyle Hammond, Timothy Jen, Rachel Goldman, Alexander Chang Due to the significant bandgap narrowing induced by the incorporation of dilute fractions of N and Bi into compound semiconductors, emerging dilute nitride-bismide alloys are of significant interest for optoelectronic devices operating in the near- to mid-infrared range. Previously, using direct measurements of N and Bi mole fractions via ion beam analysis, in conjunction with direct measurements of the out-of-plane misfit via x-ray rocking curves, we found the “magic ratio” for lattice-matching of GaAsNBi alloys with GaAs substrates. Here, we use local-electrode atom probe (LEAP) tomography to measure the stoichiometry to determine if isovalent co-alloying of GaAs with two anions (Bi, N) is limited to the replacement of As by the anions. We find that LEAP using low laser energy provides optimal conditions for probing the stoichiometry in GaAsNBi specimens. Using this data, we explore correlations between the microstructure and local electronic states, and in particular, the influence of metallic clustering. To determine the structure-property relationships, cluster analysis will be conducted on Bi atoms within the films and band structures will be calculated using the local Bi and N data as input into self-consistent Schrodinger-Poisson simulations. |
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H71.00305: Pure Spin Photocurrent in Non-centrosymmetric Crystals: Bulk Spin Photovoltaic Effect Haowei Xu, Hua Wang, Jian Zhou, Ju Li The shift and injection current mechanisms can generate charge currents under light illumination via nonlinear optical (NLO) interaction. We reveal that the similar mechanisms can be applied to spin currents and demonstrate a unified picture of NLO charge and spin currents generation. Symmetry analysis reveals that the NLO spin current can be generated under both linearly and circularly polarized light in any non-centrosymmetric materials regardless of whether time-reversal symmetry (magnetism) exists or not. And a pure spin current can be realized if the system possesses additional mirror symmetry or inversion-mirror symmetry. We apply our theory to several distinct material systems with easy optical accessibility, namely, two-dimensional transition metal dichalcogenides (TMD), anti-ferromagnetic MnBi2Te4 (MBT), and the surface states of topological material SnTe. The spin current conductivity is found to be gigantic, often exceeding the charge current conductivity. Such bulk spin photovoltaic effect (BSPE) could find wide applications in energy efficient and ultrafast spintronic devices. |
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H71.00306: Spin texture and Larmor precession caused by Rashba spin–orbit interaction for holes confined in quasi-two dimensional silicon quantum well system: crystal face dependence Shuhei Nakazawa, Katsumi Sato, Tatsuki Tojo, Kyozaburo Takeda We extend the k・p perturbation approach by taking into account the Rashba spin-orbit interaction (SOI) up to those 2nd order terms crossing with k・p term, and explore the spin texture (ST) for holes confined in the Si two-dimensional quantum well (Si 2DQW) system. The intersubband interaction (ISI) strongly modulates ST as well as the electronic structure (ES) of the heavy-mass holes (HHs), light-mass (LHs), and separate ones (SHs). We then study the Larmor precession (LP) for HHs, LHs and SHs by combining the semi-classical motion of equation with the time-dependent Schroedinger (rate) equation for the Bloch periodic part of each hole. We particularly focus on the influence by the change in crystal faces of the 2DQW system via ISI. The magnetic field applied perpendicular to the 2DQW is 47 mT, weak enough to generate LP in the simple cyclotron motion (CM). |
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H71.00307: Probing metastable space-charge potentials in a wide bandgap semiconductor Artur Lozovoi, Harishankar Jayakumar, Damon Daw, Ayesha Lakra, Carlos Meriles Despite a long history of study of space charge potentials, present models are largely based on the notion of steady state equilibrium, ill-suited to describe wide-bandgap semiconductors with moderate to low concentrations of defects. In this work we build on color centers in diamond to locally inject carriers into the crystal and probe their evolution as they propagate in the presence of external and internal electric potentials1. We observe the formation of metastable charge patterns whose shape and concomitant field can be engineered through the timing of carrier injection and applied voltages. With the help of previously crafted charge patterns, we unveil a rich interplay between local and extended sources of space charge field, which we then exploit to show space-charge-induced carrier guiding. |
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H71.00308: Giant gate-controlled odd-parity magnetoresistance
in one-dimensional channels with a magnetic proximity effect Kosuke Takiguchi, Le Duc Anh, Takahiro Chiba, Masaaki Tanaka Odd-parity magnetoresistance (OMR), in which an electrical resistance R changes as an odd function of the applied magnetic field, is a highly unconventional phenomenon only observed in a few systems.[1-3] The resistance change is tiny, reaching at most 2%, and cannot be controlled by an electrical means due to their metallicity. Here we report a new giant gate-controlled OMR observed in one-dimensional edge channels, formed by the Fermi level pinning at the side surface, in bilayer heterostructures consisting of nonmagnetic semiconductor InAs and ferromagnetic semiconductor (Ga,Fe)Sb.[4] The OMR in our system reaches 13.5% at 14 T, which is the largest value ever reported. Also, we found that simultaneous breaking of both spatial inversion symmetry and time reversal symmetry due to the strong magnetic proximity effect (MPE) at the interface between InAs/(Ga,Fe)Sb [5] is the main origin of the large OMR. We also successfully control the OMR using a gate voltage, which alters the MPE at the InAs/(Ga,Fe)Sb interfaces. |
(Author Not Attending)
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H71.00309: Ferroelectricity of stress-free pure SrTiO3 revealed by hybrid functional study Yukio Watanabe Stoichiometric SrTiO3 in the absence and presence of antiferrodistortive (AFD) distortion were calculated with multiple exchange correlation functionals, including hybrid functional. The reliability of the calculations was reinforced by the calculations of strain and AFD dependence. |
(Author Not Attending)
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H71.00310: A new criterion of accuracy of ab initio calculations of ferroelectrics and reexamination of stain-enhanced ferroelectricity Yukio Watanabe In the ab initio calculations of ferrroelectrics (FE), some exchange-correlation (XC) energy functionals such as LDA are considered to show good agreement with experiments at RT, e.g., spontaneous polarization PS, as compared with other XC functionals. This is due to the error compensation of the RT effect and, hence, will be ineffective in other situations, e.g. domain boundaries. Here, FEs under large strain at RT are approximated as those at 0 K. |
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H71.00311: Thermoelectric Performance of 2D Halide Perovskites Featuring Conjugated Ligands Sheng-Ning Hsu, Wenchao Zhao, Yao Gao, Bryan Boudouris, Letian Dou Sn-based halide perovskites for thermoelectric (TE) device application have begun to receive increased attention due to their innate low thermal conductivity as well as high electrical conductivity. Reducing the dimensionality of perovskite systems can improve the TE performance by reducing the material thermal conductivity. Two-dimensional halide perovskites not only have ultralow thermal conductivity around 0.1 to 0.17 Wm-1K-1, but also enhanced environmental stability. Combined with solution processibility and property tunability, 2D perovskites are appealing for next generation TE materials. |
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H71.00312: Intra- and Inter-Conduction Band Optical Absorption Processes in β-Ga2O3. Arjan Singh, Okan Koksal, Nicholas Tanen, Jonathan McCandless, Huili Grace Xing, Debdeep Jena, Hartwin Peelaers, Farhan Rana β-Ga2O3 is an ultra-wide bandgap semiconductor and is thus expected to be optically transparent to light of sub-bandgap wavelengths well into the ultraviolet. Contrary to this expectation, we find that free electrons in n-doped β-Ga2O3 absorb light from the IR to the UV wavelength range via intra- and inter-conduction band optical transitions. Intra-conduction band absorption occurs via an indirect optical phonon mediated process with a 1/ω3 dependence in the visible to near-IR wavelength range. This frequency dependence markedly differs from the 1/ω2 dependence predicted by the Drude model of free-carrier absorption. The inter-conduction band absorption between the lowest conduction band and a higher conduction band occurs via a direct optical process at λ ~ 349 nm (3.55 eV). We use steady state and ultrafast spectroscopy measurements to quantify the frequency and polarization dependence, and absorption coefficients of both these absorption processes. The experimental observations, in excellent agreement with recent theoretical predictions for β-Ga2O3, provide important limits of sub-bandgap transparency for optoelectronics in the deep-UV to visible wavelength range. |
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H71.00313: Influence of layer separation and doping on plasmons of double-layer α-T3 lattices Dipendra Dahal, Godfrey Anthony Gumbs, Andrii Iurov, Danhong Huang We have investigated the spectrum of alpha-T3 plasmons which arise when a pair of lattice sheets have a finite separation between them with a dielectric medium between them. The procedure we used is a calculation of the surface response function which is calculated by matching the electrostatic potential across an interface as well as relating the discontinuous electric field at each interface to its charge density on the conducting layer. Using the linear response theory, we introduce the polarization function. We determine the plasma excitations for various layer separations, dielectric media between and surrounding the layers, and doping concentrations. |
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H71.00314: Investigation of photon emitters in rare-earth-implanted hexagonal boron nitride Gabriel López-Morales, Mingxing Li, Alexander Hampel, Harishankar Jayakumar, Nicholas V Proscia, Gustavo E Lopez, Vinod Menon, Johannes Flick, Carlos Meriles We report on work towards the engineering of rare-earth-based color centers in hexagonal boron nitride (hBN), a well-known 2D Van der Waals material. Cerium (Ce3+) bombarded hBN flakes show a distribution of isolated defects with broadened spectral features (centered at ~575 nm), good optical stability and strong magneto-optical response when excited via circularly polarized light. The potential atomic nature of these color centers and their optoelectronic properties are further studied by density functional theory calculations. These results help pave the way towards defect engineering in low-dimensional materials for applications in optoelectronic devices, nanoscale sensing and quantum information processing. |
(Author Not Attending)
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H71.00315: Accurate semiempirical analytical formulas for spontaneous polarization by crystallographic parameters of SrTiO3-BaTiO3 system Yukio Watanabe Spontaneous polarizations (PS’s) of BaTiO3 (BTO) and SrTiO3 (STO) under various conditions are calculated ab initio using different exchange-correlation functionals. The extensive theoretical sets of PS vs. ion positions are found to lie on a single curve, despite the chemical differences and the wide variations of PS and lattice parameters. |
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H71.00316: Combinatorial Insights into the Structure and Properties of Cation-Disordered ZnGeN2 Celeste Melamed, Jie Pan, Allison Mis, Karen Heinselman, Rekha Schnepf, Rachel Woods-Robinson, Jacob Cordell, Stephan Lany, Eric Toberer, Adele Tamboli In this work, we present a combinatorial investigation of sputtered ZnGeN2 thin films with cross-cutting applications in fundamental materials science and development of optical devices. The II-IV-N2 materials offer potentially groundbreaking optoelectronic properties through greater chemical and structural tunability than the III-Ns. ZnGeN2 is lattice-matched to GaN and is predicted to exhibit a direct bandgap with strong absorption, but inconsistent optical properties have been reported to date. Additionally, minimal work has explored variation with cation composition. Here, we present a study of combinatorial ZnGeN2 grown by RF co-sputtering. X-ray diffraction reveals films in the cation-disordered wurtzite structure for a significant window of cation compositions and synthesis temperatures. Pawley refinements reveal a linear shift in unit cell volume with off-stoichiometry, indicating alloy-like behavior consistent with a cation antisite defect model. Finally, spectroscopic ellipsometry is performed to investigate optical properties. This study re-affirms the potential for tunability of ZnGeN2 as a direct- and wide- bandgap optoelectronic material. |
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H71.00317: Perfect electromagnetic wave absorption in black phosphorus: A multi-scale approach Mohammad Alidoust, Klaus Halterman, Douxing Pan, Morten Willatzen, Jaakko Akola Using the density functional theory of electronic structure, we compute the anisotropic dielectric response of bulk black phosphorus subject to strain. Employing the obtained permittivity tensor, we solve Maxwell’s equations and study the electromagnetic response of a layered structure comprising a film of black phosphorus stacked on a metallic substrate. Our results reveal that a small compressive or tensile strain,~4%, exerted either perpendicular or in the plane to the black phosphorus growth direction, efficiently controls the epsilon-near-zero response, and allows a perfect absorption tuning from low-angle of the incident beam to high values while switching the energy flow direction. Incorporating spatially inhomogeneous strain models, we also find that for certain thicknesses of the black phosphorus, near-perfect absorption can be achieved through controlled variations of the in-plane strain [1]. |
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H71.00318: Theoretical and experimental studies on optical spin orientation of electrons in direct and indirect bandgap AlGaAs epitaxial layers Priyabrata Mudi, Shailesh Kumar Khamari, Tarun Kumar Sharma We report the optical spin orientation of electrons in AlGaAs epitaxial layers with bandgap varying across direct-indirect cross over. Optical spin orientation spectra of AlxGa1-xAs layers with ‘x’ varying from 0.26 (direct) to 0.63 (indirect) are recorded by measuring the degree of circular polarization (DCP) of photoluminescence signal emanating from an adjacent GaAs quantum well (QW) layer. Energy of incident photons is tuned over a wide range (1.8 - 2.9 eV), to enable excitation from various valence bands in the barrier layer. A reversal of sign in DCP at a particular excitation energy is observed when the nature of band-gap is changed from direct to indirect. It is explained by proposing a theoretical model based on the capture of electrons in GaAs QW layer via different valleys in AlGaAs barrier layer. The corresponding rate equations are solved to estimate the steady state spin polarized carrier density in barrier and QW layers. Timescales of different relaxation phenomena (spin, energy, momentum) are included in the rate equations in order to explain the experimental observations. It is seen that the linear k spin splitting of X-valley governs the shape of the optical orientation spectra in indirect bandgap AlxGa1-xAs epitaxial layers. |
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H71.00319: Photoresponse study of bulk n-type doped Molybdenite (MoS2) Mehdi Pakmehr, Samira Yazdani Panah Molybdenite (MoS2) has semiconducting nature in both bulk and two-dimensional morphology, which make it useful for possible (opto) electronic device fabrications. High melting point of Molybdenite (~2500° C) make it formidable to fabricate practical optoelectronic devices (e.g. photodetector) out of it. We used Plasma Spark sintering technique to make bulk polycrystalline samples at high vacuum (10-6 torr) and pressure (10 bar). Synthesized raw samples were polished and diced into the cube. The prepared bulk cubic shape samples mounted on chip holder and four ohmic contacts made on them using silver paint. Hall measurement proved n-type nature of the samples (ne=1017 cm-3). We used chopped laser lights of different colors in conjunction with lock-in technique to measure photoresponse of our sample. We plan to present our findings at coming APS March meeting. |
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H71.00320: Highly efficient and stable flexible perovskite field-effect transistors Wenchao Zhao, Yao Gao, Sheng-Ning Hsu, Hongguang Shen, Letian Dou, Bryan Boudouris Flexible electronic devices are considered to be the technological basis of the internet of things. Via materials design and device interface engineering, the hole mobility of solution-processable perovskite field-effect transistors (PFETs) has been boosted up to over 10 cm2 V-1 s-1, which makes PFETs promising for use as high-performance transistors in future displays and sensors.[1] while high mobility values have been obtained on rigidity substrates, a new challenge is to develop high-performance PFETs on polymer substrates for flexible and wearable electronics. |
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H71.00321: Reduced graphene oxide/magnetite (rGO-Fe3O4) nanohybrids based selective room temperature H2S gas sensor. ATUL KUMAR, G. D. Varma, Anil Kumar Metal oxide/reduced graphene oxide-based hybrids have been considered as efficient materials for the sensing of toxic gases like H2S. However, these gas sensors are generally unable to perform at room temperature. In order to increase the gas sensing performance at room temperature (RT), in the present work Fe3O4 nanoparticles and rGO, having appropriate work function for the fabrication of p-n junction, have been employed to synthesize rGO-Fe3O4 nanohybrids. Thin films of the as-synthesized rGO-Fe3O4 nanohybrids and rGO have been fabricated for H2S gas sensing applications. The effect of temperature on the sensing performance has also been examined by varying temperature from 22°C to 100°C. The maximum percentage response was observed at room temperature. This sensor showed high selectivity towards H2S gas. It exhibited a very high response (40%) at 40 ppm H2S gas as compared to other toxic gases such as CO, NH3, and Cl2. Even at 100 ppm of the toxic gases, a negligible response has been observed. The present work suggests that rGO-Fe3O4 nanohybrids to be an efficient sensing material for the fabrication of highly selective room temperature H2S gas sensor. |
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H71.00322: Ultrafast optical measurements of elastic properties of 2H-MoSe2 Brian Daly, Emma Manzella, ethan murray, Madelaine Pelletier, Jacob Stuligross, Ellis Thompson, Seng Huat Lee, Ronald Dean Redwing We report ultrafast optical studies of the velocity and lifetime of 30 - 40 GHz longitudinal acoustic phonons in 2H-MoSe2. High-quality bulk single crystals of 2H-MoSe2 were synthesized by chemical vapor transport with iodine as the transport agent. Thin layers ranging from a few nm up to a few 100 nm were then mechanically exfoliated onto sapphire or Si wafers. A degenerate pump-probe experiment was performed with a Ti:sapphire laser with central wavelength varied from 760 nm to 830 nm. In the near-IR the optical absorption is strong enough that an acoustic strain pulse with frequency components greater than 40 GHz is generated. This acoustic pulse travels back and forth in the MoSe2 and causes a change in reflectivity that is measured by time-delayed probe pulses via the strong dependence of the optical properties of the crystal on strain. The measured sound velocity (2800 ±40 m/s) is in good agreement with previously published values, while the measured phonon lifetime (0.85 ± 0.2 ns) is a factor of 2 lower than a recent measurement by a related technique on a free standing membrane. We discuss implications for thermal conductivity and demonstrate GHz acoustic frequency comb behavior in the data. |
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H71.00323: Chemical Vapour Deposited Multilayer Silicon Nitride Films as Alkali Diffusion Barriers Vasumathy Ravishankar, Navaneetha Krishnan Ravichandran Silicon nitride (SiNx) is used as a diffusion barrier for alkali such as potassium hydroxide (KOH), which is often used to etch silicon. Films generally fail at pinholes present in them; while one way to prevent failure is to carefully control process parameters to deposit films with fewer pinholes, the other, less characterized method, is to deposit multiple thinner layers to achieve the same final thickness. Multilayer films deposited by chemical vapour deposition techniques are known to yield fewer pinholes, thought to be due to the misalignment of pinholes in adjacent layers. In this work, we characterize the multilayer SiNx films based on their ability to act as diffusion barriers to KOH. Here, we measure performance of these films as diffusion barriers as a function of the number of layers and thickness of each layer. We show that the ability of the SiNx multilayer structure to protect the substrate is a critically dependent on the individual layer characteristics and the deposit parameters. |
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H71.00324: Study of bulk sintered Molybdenite (MoS2) crystal quality (structural and doping level analyses) Mehdi Pakmehr, Jasper Plaisier Making Bulk Molybdenite (MoS2) crystal is a challenging task due to high melting point (~ 2500 K) of this covalent solid. One method to reach such a high temperature would be using Plasma Spark sintering technique to fabricate bulk samples at high pressure and vacuum level. The initial powder of MoS2 sintered within graphite holder while being pressed. One could control crystallization process through setting high current flow through the cell. The synthesized bulk sample structurally analyzed through common X-ray diffractometer (Cu Kα-1.54 A) as well as brilliant synchrotron based X-ray source (1.24 A). Our analyses confirm strain developed at microstructure level during the sintering process. Signatures of impurity species observed within diffraction patterns, which were obtained using synchrotron based X-ray source. Free charge carrier density due to unintentional doping (Fe, Cu) turns to be at high level (~ 1017 cm-3). We plan to present our findings at coming APS March meeting. |
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H71.00325: Non-Adiabatic Quantum Molecular Dynamics Study of Photo-Induced Three-Stage Picosecond Amorphization in Low Temperature SrTiO3 Thomas Linker, Subodh C Tiwari, Shogo Fukushima, Rajiv K Kalia, Aravind Krishnamoorthy, Aiichiro Nakano, Ken-ichi Nomura, Kohei Shimamura, Fuyuki Shimojo, Priya Vashishta Photoexcitation can drastically modify material potential energy surfaces, allowing access to hidden phases. SrTiO3 (STO) is an ideal material for photoexcitation study due to its prevalent use in nanostructured devices and rich range of functionality-changing lattice motions. Recently, a hidden ferroelectric phase in STO was accessed through weak THz excitation of polarization-inducing phonon modes. In contrast, while strong excitation was shown to induce nanostructures on STO surfaces and control nanopolarization patterns in STO-based heterostructures, the dynamic pathways underlying these optically induced structural changes remain unknown. Here, nonadiabatic quantum molecular dynamics reveals picosecond amorphization in photoexcited STO at temperatures as low as 10 K. The three-stage pathway involves photoinduced charge transfer and optical phonon activation, followed by nonlinear charge and lattice dynamics that ultimately lead to amorphization. This atomistic understanding could guide not only laser nanostructuring of STO, but also broader “quantum materials on demand” technology. |
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H71.00326: GaAs to Si Nano-Bonding at T<220°C - Optimizing Nano-Contacting and Surface Energy Engineering for Interphase Formation Siddarth Jandhyala, Aashi R Gurijala, Pranav Penmatcha, Nikhil Suresh, Amber A Chow, Shaurya Khanna, Wesley Peng, Thilina Balasooriya, Mohammed Sahal, Sukesh Ram, Robert J Culbertson, Nicole Herbots Bonding GaAs to Si yields highly efficient tandem solar cells. However, the use of high temperatures in heterostructure formation and native oxides create defects that inhibit bonding. |
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H71.00327: Surface Energy Engineering of GaAs and Si for NanoBonding in Tandem Solar Cells Pranav Penmatcha, Aashi R Gurijala, Siddarth Jandhyala, Nikhil Suresh, Amber A Chow, Shaurya Khanna, Wesley Peng, Thilina Balasooriya, Mohammed Sahal, Sukesh Ram, Robert J Culbertson, Nicole Herbots
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H71.00328: Deviation from guest dominated glass like lattice dynamics in prototypical ternary Ba filled Ni substituted Ge clathrates Amrita Bhattacharya Intermetallic guest filled clathrate cages have been identified as promising materials for thermoelectric applications. The structure, electronic structure, and phonon dynamics of type I Ba filled Ni substituted Ge clathrates are explored using density-functional theory. The formation energy of these type I clathrates (with tetrahedral vacancies) is calculated as a function of Ni substitution (x) in the framework. Ni substitution destabilized the framework vacancies resulting in a framework devoid of vacancies beyond a particular concentration of Ni substituition (for x≥3). By tuning the concentration of Ni in the framework, n type to p type doping can be achieved while retaining the compositional homogeinity. Furthermore, Ni substitution in the framework lowered the thermal conductivity of these compounds. Results of molecular dynamics simulations showed that with the increase in temperature the guest, the substitutional host as well as the host atoms rattled to collectively lower the lattice thermal conductivity of these clathrates. This is found to be contradictory to the concept of guest dominated glass like phonon dynamics in these compounds. |
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H71.00329: Mesoscale structure in phase change material (PCM) GST225 Ming Yin, Lei Wang, Timir Datta Phase change materials (PCM) were discovered by Stan Ovshinsky and his collaborators [S.R. Ovshinsky et al PRL, 21,1450 (1968)] in the 1960’s These materials are amenable to rapidly, repeatedly and reproducibly transition from crystalline to amorphous phases. The chalcogenide Ge2Sb2Te5 or GST225 is an archetypical and important example. Because, of the large contrast in electrical and optical properties of these two highly switchable but stable phases, PCMs are widely used as the active storage media in compact optical disks (DVD and DVD-R/RW) and for electronic, non-volatile random access (PCRAM) devices. We studied Phonon and the microscopic structure of GST225; a natural super-lattice type ordering in the growth habit of the material was observed. Electron microscopy reveal the atomic scale arrangement to be a 2-dimensional layered stacked structure along the orthogonal direction with submicron (~250 nm) scale periodicity. Room temperature Raman spectra, variations in chemical composition and results of electron microscopy will be presented. |
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H71.00330: Role of electronic structure on photo-catalytic behavior of carbon-nitride polymorphs Prashant Singh, Sujoy Datta, Manoj K Harbola, Duane D. Johnson Our recent implementation of van Leeuwen-Baerends (vLB) corrected LDA within full-potenital Nth-order muffin-tin orbital method shows improved band gap prediction in semicondors compared to other semi-local functionals (LDA/GGA). To validate, we demonstrate that the proposed approach accurately reproduces electronic-structure and work-function of 2D-graphene and bulk-Si, in good agreement with experiments and hybrid functionals (HSE06). A systematic band-structure analysis on cabon-nitride polymorphs was performed, and compared with hybrid functionals as implemented in existing plane wave codes. Based on our predictions, we show that the gamma phase of carbon nitride polymoprh is best candidate for photocatalysis among all. We also shows that hydrostatic-pressure further improves its photocatalytic behavior relative to water reduction. |
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H71.00331: Exploring the Additive Effects on Charge Generation in a PM6:Y6 Organic Solar Cells Awwad Alotaibi, Xaiobo Zhou, Ma Wei, Brian Collins Organic solar cells (OSCs) are promising as alternative solar energy technology, and their efficiencies are continuously increasing, currently with a record PCE~18%. The processes involved in charge generation and recombination in the active layer govern device performance. However, these processes are all entangled and hard to measure quantitatively, which limits progress in performance. We use an advanced charge extraction technique, time delay collection field, to disentangle and quantify each process occurring in a record OSC system PM6:Y6 as a function of additive, chloronapthalene, concentration. We quantify generation current and separate geminate and bimolecular recombination currents, all at operating conditions of the OSC devices. We find that geminate recombination is reduced with the additive, but generation is eventually hampered by extreme phase separation caused by the plasticizing additive. We additionally selectively excite the acceptor and donor molecules and find that Y6 generates relatively less charge than PM6, potentially due to the domain structure. Understanding these processes will help in materials design and device fabrication. |
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H71.00332: Investigating the Structural Changes of Mixed Halide Perovskites Treated with Contact Layers Tianna Green, Rebecca Belisle Mixed-halide perovskites have garnered immense scientific interest since the first implementation of the semiconductor in a photovoltaic cell in 2009. This is due to their many desirable properties such as their tunable bandgap, defect tolerance, and inexpensive fabrication. Widespread use of perovskites is hindered by the discrepancy between their theoretical and experimental efficiencies. A main contributor to this is the segregation of the halides within the perovskite forming low bandgap domains that act as traps in the material under illumination. Experimental data suggests contact layers could improve the stability of perovskites under light. Utilizing grazing-incidence wide angle x-ray scattering at the Stanford Synchrotron Radiation Lightsource, we were able to observe structural changes of MaPbBrI2 treated with either the hole-transport layer (HTL) poly(trairly amine) (PTAA) or the electron-transport layer (ETL) fullerene (C60) under continuous wave conditions in situ; with the ultimate goal of using such contacts to suppress photoinduced halide segregation. Our results indicate that contact layers play a role in the structural stability of our device. The HTL sample showed the emergence of multiple crystalline domains, while the perovskite with an ETL layer did not. |
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H71.00333: On the origin of single spin centers in hexagonal boron nitride Philipp Auburger, Adam Gali The coherently addressable single spins in two-dimensional materials such as h-BN may be the building block of ultrasensitive quantum sensors and quantum simulation devices. Recently, quantum emitting sources embedded within hexagonal boron nitride (h-BN) exhibiting optical magnetic resonance (ODMR) have been reported with isotropic g-factor and vanishing zero-field splitting [1]. Here we report strongly accumulating evidence from the results of density functional theory calculations on point defects in h-BN, based on the comparison of the observed and computed zero-phonon-line, phonon sideband in the emission, and the broadening of the ODMR line due to hyperfine interaction with the host nuclear spins, that one of the single spin centers is the carbon impurity substituting the boron site. We discuss the role of other carbon related defects in h-BN as the candidates for the other observed single spin centers. |
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H71.00334: Simulations and Experimental Results of Color-Tunability in Eu-doped GaN LEDs Kelsey Ortiz, Hayley Austin, Brandon Mitchell, Yasufumi Fujiwara, Volkmar R G Dierolf The rare-earth ion Eu3+ is well-known for its red emission at ~620 nm; however, green emission at ~545 nm also exists and is significant in Eu-doped GaN-based devices under certain current injection conditions. The relative change of intensity in the red and green emission peaks of these LEDs allows for color tuning of the overall emission, which is facilitated by pulsed current injection at various frequencies and duty cycles. This result makes the Eu-doped GaN LED an ideal candidate for a color-tunable single pixel, which could be useful for advancements in micro-LED display applications. The change in the relative emission intensity results from changes in the population ratio between the 5D0 and 5D1 excited states of the Eu3+ ions. A series of rate equations, which models each state's population, was used to explore the color tuning possibilities under different current injection conditions. Emission spectra from fabricated devices were collected under these current injections conditions, and the experimental results were compared with the simulations. |
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H71.00335: Optical properties and PL enhancement of anisotropic ReS2 Marco van der Laan, Edwin Heemskerk, Floris Kienhuis, Nella Diepeveen, Katerina Newell, Jorik van de Groep, Peter Schall Semiconducting transition metal dichalcogenides (TMDCs) is a class of materials exhibiting strong exciton binding energies of above 100 meV, which allows for novel ways of tuning the exciton resonances. Among the TMDCs, ReS2 is unique, as the anisotropic crystal structure causes multiple linearly polarized excitons to exist, which show high binding energies in bulk. However, contradicting reports exist on the number of excitons and their binding energies. Interestingly, the reported photoluminescence (PL) quantum yield (QY) of ReS2 of around 10-4 suggests that the bandgap of ReS2 could be indirect. In this work, we use differential reflection spectroscopy to elucidate the number of resolvable exciton resonances and determine their exciton binding energies. In addition, we perform power-dependent and polarization resolved PL measurements to investigate the PL saturation behaviour of various features in the PL spectra. We show 2 differently polarized excitons in differential reflectance measurements, where some higher energy peaks can be resolved that, together with the ground-state excitons, are well described by Rydberg’s hydrogenic model. Finally, we attempt various strategies to enhance the PL(QY) of few-layer ReS2 and shed light on the exact nature of its bandgap. |
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H71.00336: Unfolding the band structure of hexagonal SixGe1-x alloys Christopher Broderick CMOS-compatible group-IV active photonic devices are a key requirement for Si photonics. The indirect band gaps of Si and Ge present a significant challenge, driving efforts to realise direct-gap group-IV semiconductors. |
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H71.00337: Accurate, Ground State Electronic and Related Properties of Hexagonal Boron Nitride (h-BN) Yuriy Malozovsky, Cheick Oumar Bamba, Anthony Stewart, Lashounda Franklin, Diola Bagayoko We present an ab-initio, self – consistent density functional theory (DFT) description of ground state electronic and related properties of hexagonal boron nitride (h-BN). We performed a generalized minimization of the energy using successive, self-consistent calculations with augmented basis sets.The method leads to the ground state of the material, in verifiable manner, without employing over-complete basis sets. We report the ground state band structure, band gap, total and partial densities of states, and electron and holes effective masses. Our calculated, indirect band gap of 4.37 eV, obtained with room temperature experimental lattice constants of a = 2.504 Å and c = 6.661 Å, is in excellent agreement with the measured value of 4.3 eV. The valence band maximum is slightly to the left of the K point, while the conduction band minimum is at the M point. Our calculated total width of the valence band, total and partial densities of states are in agreement with corresponding, experimental findings. |
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H71.00338: Ab-initio Self-Consistent Density Functional Theory Description of Rock-Salt Magnesium Selenide (MgSe) Blaise Awola Ayirizia, Uttam Bhandari, Yuriy Malozovsky, Lashounda Franklin, Diola Bagayoko We report comprehensive results from density functional theory (DFT) calculations of electronic, transport, and bulk properties of rock-salt magnesium selenide (MgSe). We utilized a local density approximation (LDA) potential and the linear combination of atomic orbitals (LCAO) method. We performed a generalized minimization of the energy using successive, self-consistent calculations with augmented basis sets. Our calculated, indirect bandgap is 2.49 eV for a room temperature lattice constant of 5.460Å. We present the ground-state band structure and the total and partial densities of states, DOS and PDOS, respectively. Electron and hole effective masses were calculated for the material. Results are discussed and shown to be in reasonable agreement with available experimental data. Our calculated bulk modulus of 63.1 GPa is in excellent agreement with the experimental value of 62.8 ± 1.6 GPa. Our predicted equilibrium lattice constant, at zero temperature, is 5.424Å with a corresponding indirect bandgap of 2.51 eV. |
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H71.00339: Ab-Initio Computations of Electronic and Related Properties of cubic Magnesium Silicide (Mg2Si) Dioum Alle, Blaise Awola Ayirizia, Yuriy Malozovsky, Aboubaker Chedikh Beye, Diola Bagayoko We have performed ab-initio, self-consistent calculations of electronic, transport, and bulk properties of cubic magnesium silicide (Mg2Si). Our computations employed the local density approximation (LDA) potential of Ceperley and Alder and the linear combination of atomic orbital (LCAO) formalism. We performed a generalized minimization of the energy using successive, self-consistent calculations with augmented basis sets to reach the ground state of the material, y, without employing over-complete basis sets. For a room temperature lattice constant of 6.338 Å, our calculated, indirect band gap, from Γ to X, is 0.867 eV. We discuss the total and partial densities of states, electron and hole effective masses, and the bulk modulus. Our calculated bulk modulus of 55.96 GPa is in excellent agreement with experimental value (55 GPa). Our predicted equilibrium lattice constant and band gap, at zero temperature, are 6.2056Å and 0.947 eV. |
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H71.00340: Ab-initio computations of electronic, transport, and structural properties of zinc-blende beryllium sulfide (zb-BeS). Janee Brumfield, Yuriy Malozovsky, Diola Bagayoko We have studied the electronic, structural, and transport properties of the zinc-blende beryllium sulfide (zb-BeS), using density functional theory (DFT). We employed a Local Density Approximation (LDA) potential and the Linear Combination of Atomic Orbitals (LCAO). Our computational method leads to the ground state of the materials without utilizing over-complete basis sets. Our calculated, indirect band gap is 5.44 eV, from Gamma to a conduction band minimum between Gamma and X, for a room temperature lattice constant of 4.863 Å, is in excellent agreement with experiment which indicates the lower limit of 5.5 eV for the indirect band gap. We also report the total (DOS) and partial densities of states (pDOS), electron and holes effective masses, the equilibrium lattice constant, and the bulk modulus. Our calculated bulk modulus of 107.7 GPa is in excellent agreement with experiment (105 GPa). Our predicted equilibrium lattice constant at zero temperature is 4.814 Å. |
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H71.00341: Ab-initio Calculations of Electronic Properties of Tin Selenide (SnSe) Yuriy Malozovsky, Diola Bagayoko We present results from ab-initio, self-consistent density functional theory (DFT) calculations of electronic properties of tin selenide (SnSe) in the orthorhombic crystal structure with the space group Pnma and Pearson symbol oP8 (B16). We utilized a local density approximation (LDA) potential and the linear combination of atomic orbital (LCAO) formalism. Our calculations performed a generalized minimization of the energy to reach the ground state, as required by the second DFT theorem. This process ensures the full, physical content of our findings that include electronic energy bands, total and partial densities of states, and electron and hole effective masses. Our calculated band gaps for room temperature lattice constants a= 11.501Å, b=4.153 Å, c=4.445 Å are: indirect of 0.553 eV from Γ to Y, and a direct bang gap of 0.505 eV from Y to Y. |
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H71.00342: Subwavelength cavities via hyperbolic dispersion in two dimensional hybrid perovskites Prathmesh Deshmukh, Rezlind Bushati, Vinod Menon Two dimensional hybrid organic inorganic perovskites offer great promise in applications concerning light matter interactions due to their large oscillator strength, high binding energy and electrical isolation of the inorganic halide layers surrounded by organic cations. Recently, it was shown that the N=1,2 members of this perovskite family exhibit excitonic anisotropy in the in-plane and out of plane orientations of the crystal axis. Such anisotropic permittivity tensor naturally gives rise to a type II hyperbolic dispersion (exx=eyy<0 and ezz>0) in the visible frequency range. Here, we show the possibility of realizing subwavelength cavities using these perovskites owing to their hyperbolic dispersion. These cavities show strong field confinement with a Purcell enhancement of 11. Furthermore, they show dimension free scaling of resonant frequency, a hallmark of hyperbolic cavities. By calculating the imaginary part of Green’s function, we numerically show that such cavities exhibit large local density of photonic states. We map the isofrequency surface for in-plane and out of plane momenta by calculating the Fourier transform of the spatial fields confined in these cavities. |
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