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 AA01: V: Dopants and Defects in SemiconductorsFocus
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Sponsoring Units: DMP Chair: Chirag Gupta, University of Wisconsin - Madison Room: Virtual Room 1 |
Monday, March 20, 2023 5:00AM - 5:36AM |
AA01.00001: Emergent Atomistic Polarization Textures in Quasi-1D Hexagonal Chalcogenides Invited Speaker: Jayakanth Ravichandran The realization of topological defects such as vortices and skyrmions in magnetic and dipolar systems has allowed us to test their stability and dynamics at the microscopic limit, and also reimagine electronic and photonic functionalities in “ferroic” materials. In the case of vortex-antivortex structures, both magnetic and dipolar systems rely on boundary condition engineering and hence, their stability is dictated by narrow geometric conditions in nanoscale structures. In this talk, I will report the existence of atomic-scale vortex-antivortex dipolar structures in a quasi-1D hexagonal chalcogenide, BaTiS3 from the refined structures of X-ray synchrotron single crystal diffraction studies. BaTiS3 undergoes a series of electronic transitions from a room temperature ferrielectric phase to a vortex phase with the vortex-antivortex dipolar structures below ~250 K through a second order phase transition, and then, transforms into a lower symmetry phase below 180 K. In the vortex phase, we observe large displacements of Ti in the TiS6 octahedra of BaTiS3, comparable to ferroelectric perovskite oxides, along c-axis and in a-b plane suggesting the robustness of the polar textures. Electrical transport studies show that these phase transitions are sensitive to strain, and hence, one can infer the tunability of the electronic properties of the vortex phase. We presume the role of multipole interactions as the origin of these emergent polarization textures and note similarities in structure and electrical characteristics with charge density wave materials such as 1T-TiSe2 and Ta2NiSe5. Our work setups up complex charge density waves with d0 filling as a playground for realizing and understanding quantum polarization topologies. |
Monday, March 20, 2023 5:36AM - 5:48AM |
AA01.00002: Infrared and Raman Spectroscopy of Single Crystal (Nb,In) co-doped Rutile David Crandles, Mike Cosco, Niki Patel, Dimitrij Nuzhnyj, Victor Bovtun, Jan Petzelt, Hiroki Taniguchi Co-doped rutile single crystals of (Nb,In)0.02Ti0.98O2 (2-NITO) were grown using float zone melting. These crystals exhibit dielectric permittivity (f< MHz) significantly larger than pure rutile at low temperature, a feature which has not yet been conclusively explained. Polarized infrared and Raman spectroscopy measurements (backscattering geometry) were made on oriented (100) and (001) crystal faces at several temperatures between 4 and 300 K. The A2u and the lowest frequency Eu infrared modes both soften significantly with decreasing temperature, similar to pure rutile. Turning to the Raman spectra, co-doping produces no significant changes in the frequencies of the Raman modes. |
Monday, March 20, 2023 5:48AM - 6:00AM |
AA01.00003: Modulation of the charge state of Si-vacancy defects in diamond and their photoluminescence using high voltage nanosecond pulses Stephen B Cronin Silicon-vacancy defects have been identified as a promising optical transition for quantum communications, quantum control, and quantum information processing. In the work presented here, we demonstrate a voltage-controlled mechanism by which the photoluminescent (PL) emission from silicon-vacancy (Si-V) defects in diamond can be modulated. In particular, we can selectively produce emission from the negatively charged state of this defect (i.e., Si-V), which exhibits narrow (Γ = 4 nm) emission at 738 nm at low laser power. This approach uses high voltage (2–5 kV) nanosecond pulses applied across top and bottom electrodes on a 0.5 mm thick diamond substrate. In the absence of |
Monday, March 20, 2023 6:00AM - 6:12AM |
AA01.00004: Metastable cation vacancies in semiconducting oxides W B Fowler, Michael B Stavola, Andrew B Venzie, Amanda B Portoff Theoretical and experimental evidence has emerged [1] over the past decade that the simple cation vacancy in a number of semiconducting oxides is metastable, and that the lowest-energy configuration may have the form of cation vacancy – cation interstitial – cation vacancy. This situation may occur in crystal structures for which such a configuration has high symmetry and in which the cation interstitial forms tetrahedral or octahedral bonds with adjacent oxygens. Such structures include the Ga(1) vacancy in the β phase of Ga2O3, the cation vacancy in the α phase of Ga2O3, Al2O3 and In2O3, and the Cu vacancy in Cu2O, among others. We review and (using the CRYSTAL17 code [2]) add to the existing knowledge of this family of defects, and note that it is critical that the significance of the “shifted” structure as the equilibrium configuration be fully recognized in calculations of electronic properties, level positions, and other properties for these and similar systems. |
Monday, March 20, 2023 6:12AM - 6:24AM |
AA01.00005: Origin of layer-dependent electrical conductivity of transition metal dichalcogenides Akash Singh, Abhishek K Singh Transition metal dichalcogenide (TMD) shows layer-dependent electrical conductivity. However, there are conflicting experimental reports on the trend of conductivity, which is attributed to originating from point defects as a function of the number of layers (NLs). Using density functional theory, we analyze the layer-dependent defect thermodynamics of n- and p-type defects in MoS2 and WS2. The shallow donor levels of hydrogen defects systematically become deep with the increasing NLs to six or seven-layers and hence reduces the n-type conductivity. Moreover, the deep acceptor VS in a one-layer turns into a weak shallow acceptor for six-layers. Interestingly, from eight-layers onwards, the thermodynamic defect transition levels shift towards the conduction band due to the interplay between the bonding characteristic of the localized defect state and Coulombic repulsion of the added charge in the changing dielectric environment. The study uncovers the plausible cause of the layer-dependent electrical conductivity of TMDs. |
Monday, March 20, 2023 6:24AM - 6:36AM |
AA01.00006: Local defects in two-dimensional gallium sulfide, as single-photon emitters: first-principle evaluation. Sergey Stolbov The single photon emitters (SPE), especially those in the near-infrared (NIR) range, are the critical means for emerging quantum communication technology. In this work, the local defects in 2D GaS are evaluated in terms of the single photon emission. Based on educated guess, twelve doping-substitution defects in GaS were selected for consideration. The defects were YX, where X = Ga or S, and Y = C, Si, Ge, N, P, As (X stands for a substituted element and Y for a dopant). To evaluate stability of the defects, their formation energy and phonon spectra were calculated. For the stable defected structures, the linear response GW and the Bethe-Salpeter equation (BSE) methods were used to obtain their electronic structure and optical excitation spectra. The calculation results indicate that GaS with the CS-, NS-, and PS-defects have intense sharp excitation peaks in NIR region. The analysis of the contributions of the GW eigen states to the corresponding BSE eigen states concludes that these excitations can result in the emission with dominating narrow zero-phonon lines in the NIR region. I thus propose here the CS-, NS-, and PS-defects in the two-dimensional GaS as promising candidates for the SPE in near-infrared emission region. |
Monday, March 20, 2023 6:36AM - 6:48AM |
AA01.00007: First-principles study of the effect of polytype inclusions on divacancies in silicon carbide Victor Yu, Marco Govoni Point defects in silicon carbide (SiC), compelling analogs of nitrogen-vacancy centers in diamond, have been increasingly recognized as a candidate platform for numerous quantum technologies. Polytypism in SiC presents a material design parameter that is not available in diamond and may be utilized to create spin defects with desired properties. Using first-principles simulations based on density-functional theory, we investigated how the spectroscopic features of neutral divacancies in 4H SiC are affected by polytype inclusions of 2H, 3C, or 6H SiC. We discuss the impact of polytype inclusions on the electronic structure, zero-phonon line, zero-field splitting, and radiative lifetime of the divacancies in close proximity to interfaces between different polytypes, unveiling a promising pathway to tailoring the properties of spin defects in SiC. |
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