Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session A46: Undergraduate Research IUndergrad Friendly
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Sponsoring Units: SPS Chair: Brad Conrad, AIP Room: Room 314 |
Monday, March 6, 2023 8:00AM - 8:12AM |
A46.00001: Probing CDW states in Graphene/1T-TaS2 heterostructures using Scanning Tunneling Microscopy/Spectroscopy. Taha Kaleem, Michael Altvater, Sheng-Hsiung Hung, Nikhil M Tilak, Choong Jae-Won, Guohong Li, Sang-Wook Cheong, Chung-Hou Chung, Horng-Tay Jeng, Eva Y Andrei The transition-metal dichalcogenide 1T-Tantalum Disulfide (1T-TaS2) hosts various |
Monday, March 6, 2023 8:12AM - 8:24AM |
A46.00002: Using Scanning Tunneling Microscopy to Study the Electronic Properties of PtTe2 : A Type-II Dirac Semimetal Kenta Kodama, Luis R Carretero, Samra Tekle, Archibald . Williams, Warren L Huey, Joshua E Goldberger, Claudia Ojeda-Aristizabal, Jay Gupta Topological materials have been a widely researched topic in condensed matter physics due to their unique quantum properties observable at a macroscopic scale, protected by certain intrinsic symmetries. Here, we study a transition metal dichalcogenide (TMD) platinum ditelluride (or PtTe2), which is classified as a Type II Dirac Semimetal. Type II Dirac Semimetals are characterized by the presence of Dirac points formed by a fourfold overlap of two doubly degenerate energy bands in momentum space, where both time reversal and inversion symmetry are present. Excitations at these band crossing are not constrained by Lorentz invariance, which leads to highly tilted Dirac cones. Here, we use scanning tunneling microscopy to investigate PtTe2, which serves as a baseline for understanding the electronic structure of random Chromium alloys of the same material that introduce magnetic ordering. Current data gathered from preliminary measurements exhibit atomically flat terraces, separated by step sizes consistent with the expected atomic structure. Point defects on the surface were also seen in higher resolution images, though atomic resolution of the PtTe2 lattice require further sample preparation. Measurements were made at 100K on bulk PtTe2 crystals, which were mechanically exfoliated in UHV to produce clean surfaces. |
Monday, March 6, 2023 8:24AM - 8:36AM |
A46.00003: Fabrication of planar screening probes to study strongly correlated 2D materials such as twisted bi-layer graphene Andrew M Vincent, Jordan M Fonseca, Chadwick Evans, Arnab Manna, Arthur W Barnard
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Monday, March 6, 2023 8:36AM - 8:48AM |
A46.00004: Investigating Nanoscale Morphology and Conductivity in a PEDOT:PSS and Au Nanoparticle System Amelia Schaeffer, Nick Warren, Andrew Hyslop, Nelson Coates, Jennifer Heath Solution-processed inorganic/organic nanocomposites are strong candidates for inexpensive and scalable thermoelectric and capacitive energy storage materials. Such nanocomposites are of particular interest due to their large interface area, which can potentially be tuned to optimize desirable properties. However, the role of the interface on charge transport is neglected by standard series and parallel conduction models, limiting opportunities for improving material performance. We investigate a system of Au nanoparticles and the conductive polymer PEDOT:PSS to better understand the role of interfaces and nanostructure on charge transport. We present measurements of the morphology and nanoscale conductivity of samples of varying Au and polymer fraction using tapping and conductive AFM, and explore the role of the interfaces on the bulk material impedance. |
Monday, March 6, 2023 8:48AM - 9:00AM |
A46.00005: Green Function Approach for Calculating Surface Electronic Structure of Iron Selenide on Strontium Titanate Eli Hellmig, Hunter Sims, Tom Berlijn Electronic band structure has proven to be a useful way of observing the electronic properties of materials. Due to the cumbersome nature through which electronic band plots are generated, there is value in developing computational methods to calculate them in more complicated systems, like multilayered structures. We examine the crystalline superconductor Iron Selenide (FeSe), which exhibits a distinct shift in its surface band structure when isolated versus monolayer FeSe grown on bulk Strontium Titanate (STO) expressed through a change in superconducting temperature from the order of 10K to 70K. This case is simplified by exploiting the periodic nature of the molecular structure in crystalline materials, allowing for unit cells to be defined in different layers. For this, we turn to the use of DFT calculations to provide the basis for our model Hamiltonians, which describe the interactions between layers. Using these calculations, we modify previously written methods for calculating surface electronic structure for homogeneous materials to fit our inhomogeneous case and investigate changes to the Fermi surface in FeSe. |
Monday, March 6, 2023 9:00AM - 9:12AM |
A46.00006: Low-cost setup for determining the thickness of van der Waals materials Tedi Qafko, Andrew M Seredinski Crystalline van der Waals materials consist of layers tied together through weak van der Waals forces. They reveal new physical and electrical properties when exfoliated into thin flakes. Depending on the number of layers (i.e. thickness), the properties of these materials can vastly differ. Here, we report a low-cost procedure to determine the thickness of the different flakes by using the optical contrast predicted by a thin-film model. Thin flakes of hexagonal Boron Nitride, graphene, and mica are exfoliated onto Silicon Oxide /Silicon wafers and illuminated perpendicularly by LEDs (450nm-650nm) via an optical microscope. The contrasts between the thin flakes and the bare areas of the substrate are determined for each wavelength and compared to the model. The resulting thickness calculations are then compared to atomic force microscope results. |
Monday, March 6, 2023 9:12AM - 9:24AM |
A46.00007: Measuring the Exciton Binding Energy of Hybrid Organic-Inorganic Perovskites Michele Eggleston Hybrid organic-inorganic perovskites are being studied to explore their tunability and also their efficiency as solar cells. This project studies these perovskites using electro-absorption, where a modulated electric field applied to a sample affects its absorption of light. The measurements allow us to measure the exciton binding energy of various samples and also show that slight changes to the chemical composition of a specific sample affects its binding energy. |
Monday, March 6, 2023 9:24AM - 9:36AM |
A46.00008: Properties of carbon nanotube/alumina nanocomposites synthesized by various magnetic catalysts Suman Neupane, Steven Rhodes We report on the synthesis of carbon nanotube/alumina nanocomposites (CNTs- Al2O3) using chemical vapor deposition process. Magnetic nanoparticles including cobalt, iron, or nickel served as the catalyst for the graphitization of the carbon precursor. Incorporation of CNTs possessing remarkable mechanical, thermal, electrical, and magnetic properties onto the alumina matrix enables the development of nanocomposites with various functionalities. The structures and morphologies of the as-prepared samples were characterized by transmission electron microscope, scanning electronic microscope, X-ray diffractometer, thermogravimetric analyzer, and Mössbauer spectroscopy. The experimental results show that these as-synthesized composites contain CNTs distributed homogenously within the alumina matrix. Magnetic properties of the samples were measured using vibrating sample magnetization at room temperature and under cryogenic conditions. Such characterization is necessary for the wide-spread application of magnetic nanocomposites in different fields. |
Monday, March 6, 2023 9:36AM - 9:48AM |
A46.00009: Mechanical exfoliation of h-BN as dielectric in Josephson junction fabrication Zixuan Liang, Neda Lotfizadeh, PENG YU, Javad Shabani
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Monday, March 6, 2023 9:48AM - 10:00AM |
A46.00010: Surface reaction induced transformation of 2D-Pt-ditelluride to a 2D-monotelluride Anne R Evans
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Monday, March 6, 2023 10:00AM - 10:12AM |
A46.00011: Role of Aromatic Amino Acids in Enhancing the Optical Transmissivity of PEDOT:PSS Ege Kutlubas, Ramesh Adhikari Transparent conductors such as indium tin oxide is used in technologies where light needs to penetrate the electrode layer such as touchscreen displays and photovoltaic cells. Thin films of polymer mixture poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), one of the commonly used stable conducting polymer, has been suggested as alternative due to their high conductivity when mixed with organic solvents and high transmissivity. Here, we report that not only the conductivity but also the optical transmittivity of PEDOT: PSS can be further enhanced by introducing aromatic amino acids in the mixture before constructing thin films. We have explored the conductivity and transmissity of film with all four aromatic amino acids – Histidine, Phenylalanine, Tryptophan and Tyrosine. Using amino acids as dopants to enhance optical transmissivity of thin films presents as cost-effect and environmentally friendly alternative to develop transparent electrodes. |
Monday, March 6, 2023 10:12AM - 10:24AM |
A46.00012: Low Temperature Photoluminescence of SbPS4 Sean M Driskill, Fateme Mahdikhanysarvejahany, Vasili Perebeinos, Oliver L Monti, Brian J LeRoy, Tai Kong, John Schaibley SbPS4 is a direct gap semiconductor with a bandgap of 3 eV. It is known to have a one-dimensional van der Waals structure. SbPS4 samples were mechanically exfoliated onto SiO2 substrates. Bundles of SbPS4 were investigated with low temperature photoluminescence (PL) spectroscopy at 4 K. We investigated the excitation wavelength dependence of the PL and confirmed that the bandgap occurs near 3 eV. We observed PL from SbPS4 with a strong emission peak near 1.53 eV. Polarization dependent measurements revealed that the PL is linearly polarized along the bundle direction. I will discuss possible origins of the PL including exciton formation and defect bound emission. |
Monday, March 6, 2023 10:24AM - 10:36AM |
A46.00013: Floquet Engineered Vortex States in Dirac-like Systems Lauren I Massaro, Nancy P Sandler, Mahmoud M Asmar Periodic driving of Dirac-like materials via irradiation leads to the photon-dressing of their electronic bands and a concomitant topological phase change. Light offers multiple degrees of freedom that impact its interaction with matter. Conventionally, variations in light’s intensity, frequency, and polarization have been used to optically tune various phases of matter. However, additional degrees of tunability can arise from the spatial control of optical beams. Vortex-light beams are examples of such sources of radiation as these beams carry orbital angular momentum in addition to their polarization. This work considers a two-dimensional massive Dirac-like system subjected to a monochromatic vortex light beam. Using Floquet’s theorem, we identify the set of frequencies and polarizations for which angular momentum is conserved and find the eigenstates of the space-dependent Floquet Hamiltonian. We present a full description of the photo-induced vortex states that emerge in the irradiated system in terms of their real space extension, vorticity, and topological properties. |
Monday, March 6, 2023 10:36AM - 10:48AM |
A46.00014: Modeling the Glass Transition with a 2D Colloid Omarree Kimbrough, Orrin Shindell, Hoa Nguyen The dynamics of molecular solids near the glass transition cannot be readily observed using conventional light microscopy. To overcome this limitation, colloidal systems whose larger dispersed particles are analogous to the molecules of a dense fluid are often used to mimic molecular glasses. Experiments using colloids to investigate the glass transition in two dimensions have generally employed quasi-two-dimensional systems where a thin layer of colloidal particles is sedimented on a solid surface. In this work, we study a fully two-dimensional dense colloidal fluid tuned near the glass transition. The system consists of a two-dimensional supported fluid lipid bilayer with small lipid vesicles adhered to it via biotin-avidin bonds. The supported lipid bilayer is a two-dimensional fluid that allows the bound vesicles to move laterally while they remain constrained in-plane as a monolayer. The density of bound vesicles can be tuned by modifying the density of biotin-avidin bonds. We report measurements of the viscosity of the dense colloid, determined via Stokes-Einstein, as the system approaches the glass transition. |
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