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 B52: Electronic Structure: Theory and SpectraIndustrial
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Sponsoring Units: FIAP Chair: Guru Khalsa, Cornell University Room: Room 308 |
Monday, March 6, 2023 11:30AM - 11:42AM |
B52.00001: The Conduction Band of HfS3 and Comparison with other Quasi-1D-Transition Metal Trichalcogenides: TiS3 and ZrS3 Gauthami Viswan, Alexey Lipatov, Jehad Abourahma, Michael J Loes, Saman Bagheri, Alpha T N’Diaye, Tula R Paudel, Esha Mishra, Thilini K Ekanayaka, Mohammad Z Zaz, Jack Rodenburg, Robert Streubel, Peter A Dowben, Alexander Sinitskii Abstract: A comparison study of X-ray absorption spectroscopy (XAS) and density functional theory (DFT) has been used to understand the unoccupied energy states of HfS3. The XAS spectra at Hf 4d and S 2p core level edges indicate that the bottom of the conduction band of HfS3 is extremely sulfur weighted but also has strong hybridization between Hf-d and S-p orbitals. The density functional theory shows good agreement with the experimental results. Prior studies on TiS3 and ZrS3 have evidence of transition metal-sulfur hybridized conduction band bottom, which is Ti weighted in case of TiS3 and S weighted in case of ZrS3 [1], but there are indications that the orbital hybridization between Hf and S is stronger than in either TiS3 or ZrS3. This shows how the Group- IV transition metals, namely, titanium (Ti), zirconium (Zr) and hafnium (Hf), exhibit variations in their elemental contribution to the conduction and valence bands of the Janus layered trisulfide compounds. |
Monday, March 6, 2023 11:42AM - 11:54AM |
B52.00002: Structural study of Al(1-x)ScxN Thin Films by Mapping of Large Volumes in Reciprocal Space Anita Verma, Jakob Gollwitzer, Joseph Casamento, Guru Khalsa, Stephanie Matson, Jacob Ruff, Debdeep Jena, Andrej Singer
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Monday, March 6, 2023 11:54AM - 12:06PM |
B52.00003: Properties of incipient ferroelectrics in the vicinity of quantum critical point Anna Razumnaya Quantum paraelectricity is a type of incipient ferroelectricity where the ferroelectric order is suppressed by quantum fluctuations. The prominent quantum paraelectric, SrTiO3, is a material situated in close proximity to a quantum critical point (QCP) of ferroelectric transition in which the critical temperature to ferroelectric state is suppressed down to 0 K. However, the understanding of the behaviour of the phase transition in the vicinity of this QCP remains challenging. Here we investigate the Pb-doped SrTiO3 solid solutions, approaching the pre-critical regions of the phase diagram and study the outcome of the coexistence of quantum fluctuations and thermal motion. Using the Raman spectroscopy and dielectric measurements, we demonstrate that all samples at low doping concentration undergo the structural transition from cubic to non-polar tetragonal phase at temperature ~90 K, and to the ferroelectric orthorhombic phase at lower temperatures. This transition occurs gradually through the emergence of the polar nanoregions inside the non-polar tetragonal phase with their further expansion on cooling. Our results reveal the existence of novel structural phases in the vicinity of QCP occurring due to competition between quantum and classical regimes. |
Monday, March 6, 2023 12:06PM - 12:18PM |
B52.00004: Resolving Competing Phonon Modes in the Relaxor-type Ferroelectric Cd2Nb2O7 Daniel T Hickox-Young, Geneva Laurita, Quintin N Meier, Daniel Olds, Nicola A Spaldin, Michael R Norman, James M Rondinelli Cd2Nb2O7 undergoes a relaxor-type ferroelectric transition between 204K and 196K, drawing attention as one of the few stoichiometric relaxor ferroelectrics. Characterization of the phase transition has proved challenging due to competing contributions from two Γ-centered phonon modes (Γ4- and Γ5-). Global crystal structure refinements favor Γ5- as the primary mode, whereas first principles simulations indicate that Γ4- is more unstable. We use first principles calculations to compute energy as a function of mode amplitude and order parameter direction, discovering that the more unstable Γ4- mode also exhibits a highly isotropic energy surface. These results, along with x-ray pair distribution function measurements, point to a resolution of the competition between phonon modes, suggesting that Γ4- dominates the local structure whereas the more anisotropic Γ5- mode dominates globally. |
Monday, March 6, 2023 12:18PM - 12:30PM |
B52.00005: Mechanism for electronic and structural phase transitions in Ta2NiSe5 Weichen Tang, Zhenglu Li, Steven G Louie Ta2NiSe5 undergoes a second-order phase transition from a high-temperature orthorhombic phase to a low-temperature monoclinic phase at around 330K, accompanied by a metal-to-insulator transition. It has been intensively debated whether the transition is induced by excitonic effects or structural and lattice distortions. We use density functional theory (DFT), which in principle does not include any excitonic effects, to explore a non-excitonic mechanism to explain the electronic and structural phase transitions in Ta2NiSe5. The low-temperature monoclinic crystal structure can be obtained directly from the structure relaxation, and the corresponding electronic structure shows an M-shaped valence band top. We further study this system under S (sulfur) doping (replacing Se) and potassium dosing (introducing electron carriers). The theoretical results are in good agreement with recent high-energy X-ray diffraction (XRD) and angle-resolved photoemission spectroscopy (ARPES) data [1, 2]. Our first-principles study based on DFT suggests that a non-excitonic mechanism can explain the phase transitions in Ta2NiSe5, without invoking any excitonic effects. |
Monday, March 6, 2023 12:30PM - 12:42PM |
B52.00006: Determination of the Thermal Expansion Coefficient of Different Phases of BaTiO3 with Nanometer Resolution Bibash Sapkota, Serdar Ogut, Robert F Klie Barium Titanite (BaTiO3) exhibits several structural phase transformations over a range of 200 K, namely: rhombohedral → orthorhombic → tetragonal → cubic at temperatures around 183 K, 279 K and 385 K respectively [1]. Studies have suggested that phase transition temperature [2,3,4] and thermal expansion coefficient (TEC) [4,5] depend upon the particle sizes and the grain sizes. The ability to determine the TEC accurately across nm length scale is an important aspect in the design of miniaturized electronic devices. |
Monday, March 6, 2023 12:42PM - 12:54PM |
B52.00007: Structural ordering and IR-active vibrations within Bi2(Te(1-x)Sex)3 Craig S Knox, Matthew Vaughan, Andrew D Burnett, Mannan Ali, Satoshi Sasaki, Edmund H Linfield, Alexander G Davies, Joshua R Freeman Bismuth selenide (Bi2Se3), bismuth telluride (Bi2Te3), and their ternary alloy Bi2(Te(1-x)Sex)3 are 3D topological insulators, in addition to being room temperature thermoelectrics. Phonon modes play a key role in both these applications, and as such, an understanding of the role that these phonon modes play in the electronic and thermal transport for different compositions of the ternary alloy Bi2(Te(1-x)Sex)3 is of experimental interest. |
Monday, March 6, 2023 12:54PM - 1:06PM |
B52.00008: Influence of plastic deformation on the structural and electronic properties of SrTiO3 and KTaO3 Issam Khayr, Sajna Hameed, Damjan Pelc, Matthew J Krogstad, Raymond Osborn, Yaohua Liu, Feng Ye, Martin Greven Strontium titanate (SrTiO3, STO) and potassium tantalate (KTaO3, KTO) are incipient ferroelectrics with cubic perovskite structures at room temperature. These two materials serve as excellent candidates for plastic deformation because of their outstanding ambient-temperature ductility. Recent work on plastically deformed STO has shown an enhancement of the superconducting transition temperature and the emergence of local ferroelectricity near strain-induced self-organized dislocation walls [1]. Building on this study, we present new diffuse x-ray and neutron scattering experiments as well as charge transport data aimed to investigate in more detail the influence of compressive plastic deformation on the structural and electronic properties of STO and KTO. |
Monday, March 6, 2023 1:06PM - 1:18PM |
B52.00009: Identifying structural phases of polymorphic HfO2 by vibrational spectroscopy Sobhit Singh, Shiyu Fan, Xianghan Xu, Kiman Park, Yubo Qi, Sang-Wook Cheong, David Vanderbilt, Karin M Rabe, Janice L Musfeldt Hafnia (HfO2) is a promising material for emerging chip technology, mainly due to its robust ferroelectricity, high-κ dielectric behavior, compatibility with complementary metal-oxide-semiconductor (CMOS) technology, and suitability for negative capacitance heterostructures [1-4]. The polymorphic nature of hafnia makes the identification of its different phases challenging [4]. By means of first-principles lattice dynamics calculations combined with infrared and Raman vibrational spectroscopies, we investigate the signature vibrational fingerprints of five known phases of bulk hafnia (i.e., cubic, tetragonal, orthorhombic polar, orthorhombic antipolar, and monoclinic). We test and validate our theoretical predictions against the experimental observations and identify the vibrational spectroscopic fingerprints for each of the studied phases [5]. We especially focus on the ferroelectric phase and uncover the key polar phonon mode responsible for ferroelectric polarization in the ferroelectric hafnia. |
Monday, March 6, 2023 1:18PM - 1:30PM |
B52.00010: Correlated Disorder of the Sub-Angstrom Atomic Displacements in BaTiS3 Causes Giant Optical Anisotropy Boyang Zhao, Guodong Ren, Hongyan Mei, Vincent Wu, SHANTANU SINGH, Gwan-Yeong Jung, Huandong Chen, Raynald Giovine, Nick Settineri, Simon Teat, Raphaële Clément, Mikhail A Kats, Rohan Mishra, Jayakanth Ravichandran, Bryan C Chakoumakos Correlated disorder arising from electronic instabilities leads to emergent electronic and magnetic orderings. The connection between correlated disorder and function has been studied in magnetic, electronic, and dipolar systems, but the emergence of novel optical phenomena from correlated disorder remains poorly understood. We show unambiguous evidence of the role of correlated sub-Angstrom atomic displacements in explaining the origin of giant optical anisotropy in BaTiS3 (BTS). We carried out structure analysis by combining synchrotron single crystal X-ray diffraction (SC-XRD), scanning transmission electron microscopy (STEM) and nuclear magnetic resonance (NMR) studies supported by first principles calculations to resolve this open question. SC-XRD reveals the antipolar shifts between adjacent TiS3 chains following a P63cm space group, commensurately modulated the previously reported structure. More importantly, the refined structure of BTS shows an emergent three-fold correlated disorder of Ti a-b plane displacements towards adjacent S atoms. First principles calculations reveal preference for Γ5 distortion mode Ti displacements along the BTS a-b plane in agreement with the experiments. Finally, the magnitude of Ti a-b plane displacements strongly correlates with the increase in optical anisotropy of BTS. This study shows the broader connection between correlated disorder and function, especially in realizing emergent physical properties such as giant optical anisotropy. |
Monday, March 6, 2023 1:30PM - 1:42PM |
B52.00011: Coupling between elementary excitations in CoTiO3 David Lujan, Jeongheon Choe, Gaihua Ye, Swati Chaudhary, Cynthia Nnokwe, Martin A Rodriguez-vega, Jiaming He, Frank Y Gao, Timothy N Nunley, Jianshi Zhou, Gregory A Fiete, Rui He, Xiaoqin Elaine Li Neutron scattering experiments have revealed Dirac magnon dispersion and spin-orbit excitations in a 3D quantum XY magnet CoTiO3. Here, we investigate unique phonon properties in this material using magneto-Raman spectroscopy. The coupling between spin-orbit excitations and phonons endows large magnetic moments to two Eg phonon modes. We report the evolution of phonon spectra as a function of an external magnetic field, polarization, and temperature in CoTiO3. |
Monday, March 6, 2023 1:42PM - 1:54PM |
B52.00012: Synthesis of vanadium disulfide via chemical vapor deposition Lawrence Mubwika, Lian Li Owing to its semiconducting nature, ability to harbor intrinsic magnetic anisotropy down to the monolayer limit and valley polarization, synthesis of the 2H phase of vanadium disulfide (VS2) is of current interest. However, due to the existence of a variety of phases, as well as polymorphs for even a single given phase, the synthesis of 2H-VS2 has been challenging by chemical vapor deposition (CVD). In this work, we show the CVD growth of two crystalline structures with hexagonal and rectangular symmetries having lateral size up to a few hundred microns using optical and atomic force microscopy. Preliminary studies of the hexagonal structure via Raman spectroscopy reveal signatures of 2H phase of VS2. These findings and results from transportfrom transport, magnetic, and optical studies will be presented at the meeting. |
Monday, March 6, 2023 1:54PM - 2:06PM |
B52.00013: Spatiotemporal Study of Charge Transport in Amorphous Semiconductor Transistors Jia Yu, Yuchen Zhou, Xiao Wang, Ananth Dodabalapur, Keji Lai Due to the absence of long-range order, charge transport and carrier dynamics in amorphous semiconductors such as InGaZnO (a-IGZO) are different from conventional crystalline materials. In this work, we combine transport measurements and time-resolved microwave impedance microscopy (MIM) to study the underlying mechanisms of charge transport in a-IGZO field-effect transistors (FETs). By gradually turning on the FETs, we observed strong conductivity fluctuations near the sub-threshold regime. The typical domain size of this inhomogeneous electronic landscape is on the order of several hundred nanometers, consistent with the percolation model. We also studied the transient behavior of the MIM signals by applying square-wave-shaped gate voltages. The intrinsic charge mobility and carrier lifetime can be estimated through the purely diffusion-driven process. Our results demonstrated the crucial role of localized states and trapping/releasing process in amorphous semiconductors. |
Monday, March 6, 2023 2:06PM - 2:18PM |
B52.00014: Surface and bulk magnetic properties of a layered transition metal compound BaMn2Sb2 Bryan L Chavez, Govinda Kharal, Joanna Blawat, Scott Crittenden, Thomas M Crawford, Yanwen Wu, Rongying Jin Layered transition metal compounds have garnered attention due to their extremely rich physical properties. We present magnetic, thermal transport, and optical properties of BaMn2Sb2 single crystals with the I4/mmm structure. In addition to the G-type antiferromagnetic (AFM) ordering at 441 K, the slope of the c-axis magnetic susceptibility changes sign below Tx ~80 K. Correspondingly, the thermal conductivity is suppressed below Tx when measured under the application of a 14-Tesla magnetic field. While the second harmonic generation (SHG) measurements reveal the expected C4 surface symmetry, the polarization intensity tends to decrease with decreasing temperature below Tx. Possible origin for the observed anomalies at Tx will be discussed. |
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