Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session D12: Undergraduate Research VUndergrad Friendly
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Sponsoring Units: APS/SPS Chair: Ivy Jones, Marquette University Room: 112 |
Monday, March 2, 2020 2:30PM - 2:42PM |
D12.00001: Magnetohydrodynamic (MHD) Modeling of Kelvin-Helmholtz Instability and Associated Magnetosonic Wave Emission in Solar Coronal Mass Ejections (CMEs) Sara Butler, Hava Turkakin Interrupted telegraphy systems, regional power outages, and damaged satellites demonstrate a few of the consequences to earth technology by mechanisms that can be analyzed and prevented. The impact of solar wind on the earth and other objects in interplanetary space is relatively understudied, yet has far-reaching applications. Previous related studies have observed through close study of shear flow regions in the Solar-terrestrial environment, that Kelvin-Helmholtz Instability (KHI) and Magnetohydrodynamics (MHD) wave emissions along these boundaries may be a method by which energy is transported from flow. In order to gain a deeper understanding of the non-linear dynamics that distribute energy throughout the Solar Corona, we expand upon these previous studies to investigate the nonlinear evolution of KHI and MHD waves along the boundaries of coronal mass ejections (CMEs), large eruptions of the corona that have a significant effect on satellites, earth’s power grids, and humans in space. We utilize different criteria for measuring efficiency, including 2-D/3-D magnetohydrodynamic modeling software. We also discuss in detail the implementation of this software in our analysis about the nature of MHD instabilities in astrophysical plasmas throughout the universe. |
Monday, March 2, 2020 2:42PM - 2:54PM |
D12.00002: Cradle-to-Grave Evolution and Explosiveness of the Magnetic Field from Bipolar Ephemeral Active Regions (BEARs) in Solar Coronal Holes Caroline Nagib, Navdeep K. Panesar, Ronald L. Moore, Alphonse C. Sterling We report on the magnetic evolution of magnetic-explosion eruption production of each of seven BEARs observed in on-disk coronal holes in line-of-sight magnetograms and in coronal EUV images. One of these BEARs produced no eruptions. The other six BEARs display three kinds of magnetic-explosion eruptions: (1) blowout eruptions, (2) partially-confined eruptions, (3) confined eruptions. The seven BEARs are a subset of 60 random coronal-hole BEARs, with visually estimated emergence phases. In this work, we obtain a reliable determination of when the emergence phase ended by finding the time of the BEAR’s maximum minority flux from a time plot. These plots show: (1) none of the seven BEARs had an inside eruption while the BEAR was emerging, and (2) for these seven BEARs, the visually-estimated emergence end time was never more than six hours before the measured time of maximum minority flux. Our findings support that a great majority of the explosive magnetic fields from BEARs in coronal holes are prepared and triggered to explode by magnetic flux cancellation, and that such flux cancellation seldom occurs inside an emerging BEAR. |
Monday, March 2, 2020 2:54PM - 3:06PM |
D12.00003: Magnetic and Electronic Structure of CuTeO4 Zubia Hasan, Thao Tran, Tyrel McQueen Cu2+ based materials have been extensively studied over the past decades due to their importance in high temperature superconductivity as well as their potential as quantum spin liquids. Recently,1 CuTeO4 has been proposed as a candidate material that combines a geometrically frustrated triangular lattice with potential high temperature superconductivity upon doping. To date, CuTeO4 has only been made as a secondary phase while making other Copper Tellurates, under extreme hydrothermal conditions over months 2. We developed a novel method of synthesizing CuTeO4 in single phase form, enabling us to characterize its physical properties by magnetization, heat capacity, and neutron diffraction. CuTeO4 was initially predicted to have a quasi-2D Neel ground state. Our magnetic susceptibility data shows no long range ordering with an upturn at T=50K and an intriguing hump around T=120K indicative of low dimensional antiferromagnetic interactions. Heat capacity data shows no magnetic transition at T=50K, an inconsistency that needs to be explored further. With the bulk characterization to date, CuTeO4 seems to be a prime candidate for low-dimensional magnetism. |
Monday, March 2, 2020 3:06PM - 3:18PM |
D12.00004: Properties of Magnetic High-Entropy Alloys Valeria Rosa Rocha, Abby M Nash, John-Paul E. Cesare, Troy Messina Magnetic high-entropy alloys are a promise for many fields. From cryogenic to aircraft and spacecraft applications, the possibilities are varied but one thing is necessary: we must have a better understanding of the properties of these materials in order to put them to good uses. Korman et al. made predictions for the Curie Temperatures (Tc) of HEAs of the form CrxCoFeNiQx with Q being Pd, Cu, Ag, or Au. In our study, we focused on the Pd alloys varying both Cr and Pd in order to check the accuracy of the Tc predictions. Using the “Treasure Maps” provided by Korman et al. we chose combinations of Cr and Pd that were predicted to have a Tc near room temperature. Based on our work, we found the maps to be very reproducible with the procedure used, which is further explained in this presentation. |
Monday, March 2, 2020 3:18PM - 3:30PM |
D12.00005: Magnetic Heat Capacity Characterization of Magnetite Silvia Sherman, Stephen A Tsui We investigate the magnetic and thermal properties of magnetite using both vibrating sample magnetometry (VSM) and heat capacity measurement. Magnetite undergoes the Verwey transition, which is a structural phase transition near 120 K. The magnetization behavior vs. temperature differs between field cooled (FC) and zero field cooled (ZFC) measurements in the VSM, due to the preferential alignment of the magnetic spin moments with respect to applied magnetic field. The application of magnetic field also contributes to an enhancement in the heat capacity. In this study, we investigate the behavior of the heat capacity of different specimens of magnetite under these FC and ZFC conditions. |
Monday, March 2, 2020 3:30PM - 3:42PM |
D12.00006: H-T phase diagram of antiferromagnetic topological insulator MnBi2Te4 under hydrostatic pressure to 2.5 GPa Rakin Numair Baten, Timothy A Elmslie, Derrick VanGennep, James J Hamlin MnBi2Te4 is a layered compound that is an intrinsic antiferromagnetic topological insulator. Metamagnetic transitions have been observed at 3.2 T and 7.8 T at ambient pressure. By compressing the unit cell with hydrostatic pressure and applying a magnetic field we can track these metamagnetic transitions and investigate the magnetic ordering. In this talk I will present transport data and temperature-field phase diagrams of MnBi2Te4 single crystals up to 2.7 GPa and 9 T. |
Monday, March 2, 2020 3:42PM - 3:54PM |
D12.00007: Modeling Hyperfine Coupling in Molecular Magnets Cong Hu, Jia Chen, Xiaoguang Zhang Nuclear or electron spins of magnetic molecules are promising qubit candidates1. Electron spins are advantageous due to faster operational times, but they decohere faster due to stronger coupling to environment. This project investigates hyperfine couplings in four vanadyl complexes with long decoherence times as qubits2 by electron structure calculations. In all complexes, electron spins are localized on V4+ ion. Using the analytic derivative method based on density functional theory, the Fermi-contact and spin-dipole interactions were calculated. Total hyperfine coupling to vanadium nuclear spin is compared to experiment; Using hybrid functional, good agreement can be achieved. Due to the localized nature of electron spins, the Fermi-contact interaction between an electron spin and hydrogen nuclear spin is only strong for the smallest complex. Hyperfine coupling to hydrogen nuclear spins as the main source of electron spin decoherence can be modeled by spin-dipole interactions. |
Monday, March 2, 2020 3:54PM - 4:06PM |
D12.00008: Mössbauer spectroscopy of iron oxide nanoparticles containing both magnetite and maghemite Jeremy Winsett, saeed kamali, Suman Neupane Iron oxide nanoparticles are available in two common phases, including magnetite (Fe3O4) and maghemite (Fe2O3). Upon exposure to oxygen atoms, the magnetite phase readily oxidizes into the maghemite phase with the partial conversion of ferrous ions into ferric ions. We report on the approach to determine the ratio of magnetite and maghemite in iron oxide nanoparticles synthesized by the hydrothermal process. The crystallinity of these nanoparticles has been investigated by X-ray diffraction studies and transmission electron microscopy observations. The hysteresis loops of the iron nanoparticles demonstrated the “S-shaped” pattern corresponding to superparamagnetic behavior. The Mössbauer spectrum of the sample is compared with the theoretically predicted model to determine the contributions from magnetite and maghemite. Such characterization is necessary for the synthesis of magnetic nanoparticles of uniform size with potential for biomedical applications. |
Monday, March 2, 2020 4:06PM - 4:18PM |
D12.00009: Computational Modeling of Magnetorheological Elastomers Tong Dang, Andy T Clark, Jiajia Li, David Marchfield, Kristen S. Buchanan, Xuemei Cheng Ultra-soft polydimethylsiloxane (PDMS) based magnetorheological elastomers (MREs) are composite materials of polymeric matrix with embedded micro- or nano- sized ferromagnetic particles. They are promising candidates for dynamic cell culture substrata due to their magnetic field dependent mechanical properties. In this work, we have used a two-step, multi-scale approach to model the complex magnetic reversal behavior of MREs. Micro-magnetic simulations were performed using MuMax3 to obtain a detailed description of the magnetic reversal process of individual Fe particles. The micromagnetic modeling results are then used as input parameters for a particle interaction model that includes dipolar interactions and elastic deformations. This model was used to study the magneto-mechanical interactions between a large collection of particles and their surrounding elastomer matrix, which provides insight into the complex magneto-mechanical interactions of MREs. |
Monday, March 2, 2020 4:18PM - 4:30PM |
D12.00010: CsPbBr3 Perovskite Quantum Dots as Single Photon Sources Georgia Nelson, Giorgio Adamo, Cesare Soci, Michael Lim Cesium Lead Bromide (CsPbBr3) Perovskites Quantum Dots (PQDs) are zero-dimensional semiconducting particles with tunable optical properties. We are interested in PQDs as possible single photon sources with applications in quantum computing and quantum cryptography. We have successfully fabricated CsPbBr3 PQDs and measured their photoluminescence intensity as a function of wavelength. As temperature is varied from 77K to 293K, the central wavelength undergoes a blue-shift. The fabricated CsPbBr3 PQDs are stable at 77K and 293K. Diluting the solution used in fabrication should allow us to create samples of individual, spatially-resolved quantum dots, which can then be verified with g(2) measurements. |
Monday, March 2, 2020 4:30PM - 4:42PM |
D12.00011: Quantum entangled breathers in Goldilocks quantum cellular automata Haley Cole, Matthew Jones, Logan Hillberry, Mina Fasihi, Lincoln Carr We conducted robustness studies of quantum entangled breathers (QEBs) to evaluate their stability. QEBs are an emergent dynamical structure appearing in a continuous time generalization of Goldilocks quantum cellular automata. This system is a qubit spin chain on which sites evolve according to a local unitary operator if and only if 2 or 3 sites in a 5 site neighborhood are spin-up. The QEB is a quantum entangled generalization of a discrete breather or excited bright soliton on a lattice, a famous and robust classical solution to nonlinear wave equations. We consider four sources of noise: uniform and non-uniform spatial noise in the state; uniform spectral noise in the state; perturbations to the closed system Hamiltonian; and open quantum system evolution including T1 and T2 decoherence processes. We find that QEBs present a robust signal of quantum complexity in a simple system that can be studied on a wide variety of quantum simulators. |
Monday, March 2, 2020 4:42PM - 4:54PM |
D12.00012: Synthesis and Characterization of Quantum Dots Based on Transition Metal Dichalcogenides Pedro Juan Rodríguez Fernández, Nalaka A Kapuruge, Humberto Gutierrez Atomically transition metal dichalcogenides (TMDs) have attracted a significant attention due to their novel and promising physical properties. However, Quantum Dots (QDs) based on TMDs have been less studied. QDs present size-dependent optical and electronic properties due to quantum confinement of electrons and phonons. Consequently, they have potential applications in medicine, renewable energy, and electronics, among others. In this presentation we will describe a simple synthetic approach to produce TMD-based QDs as well as the study of their physical properties. The synthesis involves mechanical rupture of large TMD flakes using a high power ultrasonic horn, bath sonication and/or thermal reflux. Subsequently, QDs of different sizes are selected by centrifugation. The effect of different parameters such as ultrasonic power, time, solvent type and centrifugation conditions on the final size distribution were studied. The morphology of the TMD fragments was studies by scanning electron microscopy and atomic force microscopy. The optical response of the as-prepared materials was evaluated using optical absorption spectroscopy, photoluminescence and Raman spectroscopies. |
Monday, March 2, 2020 4:54PM - 5:06PM |
D12.00013: Single Hole Based Magneto-Impedance Biosensor for Particle Detection Baylee Senator, Valery Ortiz Jimenez, Manh-Huong Phan GMI (giant magneto-impedance) sensors have been used for biomedical applications that require maximum sensor detection sensitivity for accurate magnetic field detection. To create better biosensors, Fe3O4 nanoparticles are applied to holes drilled into a ribbon-based GMI biosensor which should increase the sensor detection sensitivity. A focused ion beam is used to drill various sized holes – 3, 4, 5, 7, and 10 μm diameters – into soft ferromagnetic Metglas® 2714A ribbons. The sensor sensitivity of these samples is measured as-cast, with holes, and with iron oxide nanoparticles at frequencies between 50 and 175 MHz. The addition of iron oxide nanoparticles has shown to increase the sensor sensitivity of the samples while the GMI ratio decreases. In conclusion, the sensor detection sensitivity of ribbon-based GMI biosensors improves when the iron oxide nanoparticles are applied and measured between 110 and 150 MHz, therefore, creating biosensors with greater detection sensitivity. The maximum sensitivity measured for the ribbon as-cast was 60 %/Oe, this increased to 105 %/Oe when the iron oxide nanoparticles were applied. |
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