Bulletin of the American Physical Society
2021 Virtual Conference for Undergraduate Women in Physics
Friday–Sunday, January 22–24, 2021; Virtual
Session U02: Solid State Materials and Applied Physics IIInteractive Live
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Chair: Masha Kamenetska, Boston University |
Sunday, January 24, 2021 12:00PM - 12:10PM |
U02.00001: Jahn Teller Effects In Cubic ScF3 Domitiler Orori Jahn-Teller effects arise in a crystal if distortions are considered on either the octahedral or tetrahedra complexes. This is a non-volatile approach in tailoring materials properties. ScF3 is a material that has arouse special interests based on its Negative thermal expansion (NTE) behaviour. To this date, little is understood on the interplay between Jahn-Teller effects and NTE. The researchers herein, give a focus on how the Jahn-Teller interactions alter the chemistry of this crystal. We employed Density Functional theory as implemented in the Siesta method coupled with mild distortions on the octahedra complex. The results herein go along way in exploring non-volatile approaches in engineering materials. Experimentalists can use this as a back bench in designing materials for novelty. Key words: DFT, ScF3 , NTE, Jahn-Teller distortions. [Preview Abstract] |
Sunday, January 24, 2021 12:10PM - 12:20PM |
U02.00002: Assessing the Transition from GdCuAs2 to GdCuP2 Using DFT Calculations Clara Larson h $-abstract-Last summer, I used supercomputing resources at the University of Minnesota's MSI to study the transition from the compound GdCuAs2 to GdCuP2, where arsenic is replaced with phosphorus in the crustal structure. DFT calculations were run to study the electronic band structures, instabilities and structural distortions of GdCuAs2 and GdCuP2. We are interested in the transition between the two compounds because both structures have square nets of atoms in their structures. This configuration has been associated with crossings in its electronic band structure which suggest potential topological phases. Our results suggest that the band crossings in GdCuAs2 sit below the fermi level and are mostly occupied by p- and d- orbitals of Arsenic atoms in the square net. Additionally, we found that GdCuAs2 is more stable than GdCuP2 due to the presence of arsenic (rather than phosphorus) in the square net, and that the larger GdCuAs2 crystal unit cell size has a negligible effect on structural instabilities. Our distortion calculations suggest that square nets and zig-zag chains are the most stable configurations of Arsenic atoms in GdCuAs2 and GdCuP2, respectively. To investigate the topology of the crossings, further work is needed./abstract-$\backslash $pard$\ [Preview Abstract] |
Sunday, January 24, 2021 12:20PM - 12:30PM |
U02.00003: CFD Validation and Replication of Turbulent, Compressible Shear Layer Data Lucy Brown, Kristen Matsuno, Sanjiva Lele Shear layers are a phenomenon in fluid mechanics in which two flows traveling at different velocities interact to form a spatially-developing region of mixing and turbulence. Shear layers have many engineering applications, including high-speed jets and scramjet engines. As flows increase in speed, their behavior is complicated by the effects of compressibility. One key parameter in this study, the convective Mach number, is a measure of the difference in speeds of the two flows. Previously, researchers at the University of Illinois Urbana-Champaign (Kim, Elliott and Dutton, AIAA J, 2020) ran laboratory experiments of shear layers at various convective Mach numbers. My work investigates the best techniques through which we can replicate experimental results using computational fluid dynamics (CFD). Through this investigation, I validate Kim, Elliot, and Dutton's results through various measures of shear layer thickness, Reynolds stresses, and normalized velocity profiles. Additionally, my results provide insight into which turbulence models best represent compressible shear layers. Finally, I describe my CFD process from meshing to post-processing in MATLAB. Through this project, I aim to expand the literature on turbulent, compressible shear layer modeling. [Preview Abstract] |
Sunday, January 24, 2021 12:30PM - 12:40PM |
U02.00004: Absorption coefficient computation for triple delta-doped wells in AlGaAs / GaAs in presence of electric and magnetic fields. Erika Cecilia Carrillo Trejo, Juan Carlos Martínez Orozco, Antonio Del Río De Santiago The optoelectronic properties of nanostructured quantum systems are of great interest both from the point of view of basic physics and for their potential applications, specifically in recent times there is much interest in systems that operate in the terahertz region. In this case, the intersubband transitions of the semiconductor quantum wells based on the AlGaAs / GaAs heterostructure, due to the band offset, are precisely in this range. So in this work we present the calculation of the electronic structure, and the intersubband absorption coefficient for a triple delta-doped well as a function of electric and magnetic fields applied in the growth direction and in-plane, respectively. We found that the asymmetry in the considered charge carrier densities, which produce the profile, and the electromagnetic fields allow appreciable changes in both, the magnitude and in the location of the resonant peaks of the absorption coefficient. Thanks to the SEP-CONACyT A1-S-8842 project. [Preview Abstract] |
Sunday, January 24, 2021 12:40PM - 12:50PM |
U02.00005: Controlling the magnetic properties of a ferromagnetic film using a ferroelectric layer Aarushi Khandelwal, Pingfan Chen, Gan Moog Chow Magnetoelectric multiferroics are materials that simultaneously support both ferroelectricity and ferromagnetism. They are of interest for new devices because they allow multiple tunable functionalities to be incorporated in the same material and provide new degrees of freedom. One way to engineer such materials is to construct a composite multiferroic, a heterostructure of a ferromagnetic layer and a ferroelectric layer where the magnetoelectric effects originate from the interfacial coupling. This talk will characterize the nature of this interfacial coupling in a multiferroic heterostructure of LSMO/PZT. It will elaborate on the two main coupling mechanisms present: oxygen octahedral rotation and magnetoelectric coupling. It will also describe the techniques and models used to grow the samples and quantify the impact of these coupling mechanisms on the heterostructure's structural, magnetic, and electronic properties. Thus, it will explore how the magnetic properties of the LSMO layer (Curie temperature, magnetic moment per Mn ion, coercivity, and magnetoresistivity) can be tuned using the ferroelectric PZT layer. Finally, it will also summarize the potential applications of such a heterostructure in spintronics, data storage, and magnetoresistive sensors. [Preview Abstract] |
Sunday, January 24, 2021 12:50PM - 1:00PM |
U02.00006: Search for -- and growth of -- atomic-cage thermoelectrics Sarah Longworth In this project, we are growing Zn and Al atomic-cage thermoelectrics. Thermoelectric materials convert thermal energy directly into electrical energy by utilizing the Seebeck effect, wherein a voltage is generated by a thermal gradient. Thermoelectrics are particularly useful in that they can be used to harness waste heat generated in the production and consumption of other energy processes. The cage structure of the material, comprised of heavy ions ``rattling'' within void spaces of the crystal, allows for an increase in the thermoelectric efficiency of the material by interfering with heat conduction via vibration and allowing for conduction via electrons. We are investigating the family of materials with composition \textit{MM'}$_{\mathrm{2}}X_{\mathrm{20}}$ ($M, M'=$ transition or rare earth metals and $X=$ Zn, Cd, or Al) which have the desired cage structures and have already been shown to exhibit thermoelectricity. We are currently utilizing the self-flux method in order to synthesize high-quality crystals of novel materials to be analyzed for thermoelectric properties. Composition and structure of prepared crystals is investigated using energy dispersive spectroscopy (EDS) as well as both powder and single-crystal x-ray diffraction (XRD). Crystals exhibiting promising cage structures will be sent to the National High Magnetic Field Laboratory in Tallahassee, FL to be tested for thermoelectric properties. [Preview Abstract] |
Sunday, January 24, 2021 1:00PM - 1:10PM |
U02.00007: Using non-equilibrium Molecular Dynamics to gain insight into the negative capacitance regime in ferroelectrics. Kelli Ann Lynch, Inna Ponomareva The negative capacitance regime has potential for overcoming the Boltzmann tyranny, which limits performance for conventional transistors. Ferroelectrics are of interest for negative capacitance applications due to their potential energy profile. When minimized, the free energy results in an equation of state with an S-shaped dependence of polarization on electric field, whose central region is thermodynamically unstable. Experimental detection of negative capacitance seems to suggest that a ferroelectric can be ``tricked" into entering this region. Our investigation aims to provide a clearer understanding of the underlying physical mechanism that drives ferroelectrics into the negative capacitance regime. Technically, we simulated PTO bulk and 39-nm thick film subjected to electric field using classical Molecular Dynamics with the interaction modeled by a first-principles effective Hamiltonian. We will present data for both bulk and film, concluding that the ferroelectric avoids the forbidden region even with high rates of electric field application and epitaxial compressive strain. However, negative capacitance was observed in the dependence of polarization on internal electric field, with the effects of the residual depolarizing field included. Finally, we will conclude that it is possible to tune the negative capacitance regime using the surface charge compensation and amplitude of the applied electric field. The work is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under grant DE-SC0005245. [Preview Abstract] |
Sunday, January 24, 2021 1:10PM - 1:20PM |
U02.00008: Photoluminescence of Sulfur Doped Dysprosium Oxide Sadie Nickles Rare-earth (RE) ions, such as Dysprosium, have well-defined luminescent properties that have been studied successfully in the past by using glass structures doped with these RE ions, typically in oxide form, such as Dy2O3. The technique of photoluminescence, where laser light is used to excite the sample, and studying the emitted light from the sample, the dominant electronic transitions in the samples can be examined and their suitabilit determined for applications in solid-state lasers or light-emitting devices. Little, if any, research has been done on the powder form of Dysprosium Oxide, which is more practical for real-life applications such as those involving a solid-state laser or other light emitting devices. Using previous research on these oxides in our laser lab as a basis for this project, a collaboration was undertaken with the chemistry department in order to sinter new samples where sulfur is incorporated into the structure of the pure Dysprosium oxide (Dy20(3-x)Sx) in an attempt to enhance its photoluminescence. This was done in order to enhance its applicability for solid-state laser materials. The photoluminescence spectra of the samples will be collected using laser spectroscopy with an argon-ion laser and a standard GaAs detector [Preview Abstract] |
Sunday, January 24, 2021 1:20PM - 1:30PM |
U02.00009: Solvent Dynamics and Confinement Effects around an Intrinsically Disordered Protein, }$\beta $\textbf{-Casein, Revealed by using Spin Probe EPR Spectroscopy Erin Neely, Wei Li, Kurt Warncke Electron paramagnetic resonance (EPR) spectroscopy with the spin probe TEMPOL, a paramagnetic nitroxide with detectable rotational motion, is used to study the temperature-dependent structure and dynamics of the solvent phases surrounding the protein $\beta $-casein in solution at temperatures from 195-265 K. We have previously studied ordered globular proteins; by contrast, $\beta $-casein is an \textit{intrinsically disordered} protein (IDP), i.e. it has no fixed, well-defined structure. The goal of this project is to determine whether and how the EPR spectra of the TEMPOL-$\beta $-casein systems differ from those of systems with more ordered proteins. Experimental spectra have already been collected for these systems with and without added DMSO cosolvent over the temperature range. By simulating these experiments using Matlab and finding the parameters for best fit of the experimental spectra, we can determine the physical parameters of these systems such as TEMPOL rotational correlation time, linewidth and component amplitudes. Comparing $\beta $-casein's EPR spectra and parameters with those of globular proteins will offer insight into how IDP's interact with and structure their solvent environment. Insights into the solvent-protein structures and dynamics that control aggregation and reactivity will be gained. [Preview Abstract] |
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