Bulletin of the American Physical Society
2021 Annual Meeting of the APS Four Corners Section
Volume 66, Number 11
Friday–Saturday, October 8–9, 2021; Virtual; Mountain Daylight Time
Session E03: Low Dimensional Systems and their Applications |
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Chair: Shashank Misra, Sandia National Laboratory |
Friday, October 8, 2021 3:15PM - 3:39PM |
E03.00001: Controlling excitons in 2D semiconductor heterostructures. Invited Speaker: John Schaibley Two dimensional (2D) semiconductor transition metal dichalcogenides (such as MoSe$_{\mathrm{2}}$ and WSe$_{\mathrm{2}})$ host excitons with large 500 meV binding energies that interact strongly with light. In recent years, the development of bilayer heterostructures that host spatially indirect interlayer excitons has led to the discovery of moire' excitons, and control of valley polarized exciton currents. I will discuss our recent progress investigating the temperature dependent moire' trapping and deterministic nanoscale trapping of interlayer excitons in MoSe$_{\mathrm{2}}$-WSe$_{\mathrm{2}}$ heterostructures. In particular, we report a transition temperature of the interlayer exciton photoluminescence intensity that has opposite behaviors for heterostructures with near 0 and near 60 degree relative twist angle. I will also describe our recent demonstration of nanoscale interlayer exciton traps that have potential applications to quantum information science applications. [Preview Abstract] |
Friday, October 8, 2021 3:39PM - 4:03PM |
E03.00002: Computational Discovery, Synthesis, and Functionalization of 2D Materials Invited Speaker: Arunima Singh Less than 5 {\%} of the \textgreater 6000 theoretically predicted and promising two-dimensional (2D) materials have been experimentally synthesized. In this talk, I will present a density-functional theory based framework that can be used to identify suitable substrates that enable growth and functionalization of as-yet-hypothetical 2D materials. We have applied this formalism to identify substrates for 2D group-III-V materials, validated it against experimental synthesis of 2D MoS$_{\mathrm{2}}$ and integrated the results from the framework with phase-field models to predict the micro-structure of graphene on various metallic substrates.$^{\mathrm{\thinspace }}$ We are currently applying this strategy for a high-throughput screening of substrates for the thousands of as-yet hypothetical 2D materials. In order to automate the steps associated with the search such as generation of heterostructures, creation of input files, submission of runs on computing resources, post-processing of simulations, error management and curation of key properties in an open-source database, we have developed open-source python-packages. The high-quality electronic structure data and physio-chemical properties of 2D materials-substrate interface emerging from this study will provided an invaluable theoretical input to 2D materials growers as well as serve as a critical atomic-scale input for multi-scale studies leading to an accelerated growth and functionalization of 2D materials. [Preview Abstract] |
Friday, October 8, 2021 4:03PM - 4:15PM |
E03.00003: Material Properties of Widegap AlGaN for use in Power Electronics Nicholas Baldonado, Julia Deitz, Boris Kiefer Materials with a significantly larger bandgap than silicon have emerged as a competing material platform for power electronics, including the development of light emitting UV diodes, materials with higher break-down voltages, and shorter switching times. Here we present results from parameter-free first principles density-functional-theory (DFT) computations on AlN, AlGaN, and GaN insulators and the effect of p- and n-doping on electronic, magnetic, and optical properties. Our computations benefit from the improved description of optical properties in materials using a self-consistent ACBN0 (Hubbard-U) approach. The preliminary results strongly suggest that both n- and p- dopants condense in proximity of defects such as surfaces, and interfaces. The detailed analysis of the associated electronic structure shows that the most stable surface truncations are metallic, changing the fundamental classification of these materials from insulating to conducting. We will discuss the effect of the predicted bandgap closure for applications of these materials in power electronics devices. Sandia National Laboratories are managed and operated by NTESS under DOE NNSA contract DE-NA0003525. [Preview Abstract] |
Friday, October 8, 2021 4:15PM - 4:27PM |
E03.00004: Engineering Defects in AlGaN for Advanced Information Processing Jeremy Kamin, Dr. Julia Deitz, Dr. Boris Kiefer It is well known that defects can fundamentally change the electronic structure of materials and thereby enable novel applications. For example, point defects in diamond (NV-centers) create novel electronic states with uses in quantum computing and quantum sensing. However, diamond is costly and comparatively difficult to manipulate. Here we report on density-functional-theory (DFT) assessment of point defects in AlN, AlGaN, and GaN and their effect on electronic, magnetic, and optical properties. Dopants were selected by minimizing ionic radii mismatch with Al and Ga, low spin-orbit coupling and high abundance of (nuclear) spin-singlet isotopes. Among the most promising elements are Si and Cr. Our preliminary results show that Gavacancies alone may be beneficial for spin-qubit design. Combining Si-dopant and Ga-vacancy may be beneficial for robust spintronics. Similarly, Cr doping may find application in spin-based devices and technologies. Therefore, defect engineering in widegap insulators appears as a unifying materials platform that can support a wide range of spin-based technologies. Sandia National Laboratories are managed and operated by NTESS under DOE NNSA contract DE-NA0003525. [Preview Abstract] |
Friday, October 8, 2021 4:27PM - 4:39PM |
E03.00005: Testing the Optical Properties of Perovskite and ZnCuInS/ZnS Quantum Dots for Use in Optical and Microfluidic Environments Daniel King, John Colton, Emma McClure, Derek Sanchez Semiconductor nanocrystals (quantum dots) can potentially be used as accurate temperature sensors for microfluidic systems. In previous research, our group used the emission spectra of cadmium telluride quantum dots to train a neural network to predict temperature. Building on that research, we have measured the emission spectra of perovskite quantum dots at various temperatures, and have determined they would unfortunately not be suitable for such an application, due to inconsistency in their optical spectra. We are now currently in the process of studying ZnCuInS/ZnS quantum dots to similarly determine their viability in filling this role. [Preview Abstract] |
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