Bulletin of the American Physical Society
Joint Fall 2021 Meeting of the Texas Sections of APS, AAPT, and SPS
Volume 66, Number 10
Thursday–Saturday, October 21–23, 2021; Houston; Central Time
Session J04: Condensed Matter, Plasma Physics & Computational Physics I |
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Chair: Tej Limbo, UHCL Room: STEM 3133 |
Friday, October 22, 2021 10:00AM - 10:36AM |
J04.00001: Orbital Hall effect and its detection Invited Speaker: Hyun-Woo LEE The orbital Hall effect refers to the electrical generation of an orbital angular momentum current in a transverse direction. The orbital Hall effect can arise intrinsically through Berry curvature and in certain materials including 5d transition metals, the orbital Hall effect plays a crucial role for the generation of the spin Hall effect. This talk briefly summarizes the present theoretical understanding of the orbital Hall effect and presents recent progresses in the experimental detection of the orbital Hall effect. [Preview Abstract] |
Friday, October 22, 2021 10:36AM - 11:12AM |
J04.00002: Studying phonons and electrons in 2D materials by resonance Raman spectroscopy. Invited Speaker: Marcos Pimenta Electron-phonon (el-ph) scattering processes in 2D heterostructures can emerge from the coupling of atomic layers and are essential for describing their physical properties. The additional possibility of controlling the twisting angle between layers opens new possibilities for tunable devices. Raman spectroscopy is a fundamental tool to investigate el-ph interactions, and the use of multiple laser energies allows the study of the resonance mechanisms. In this seminar I will first present Raman results in samples of twisted bilayer graphene (TBG) with different twisting angles and measured using many different laser lines. Results reveal that there are two different resonance processes: the intralayer process, where the el-ph scattering occurs in a single graphene layer and the other layer imposes a periodic potential that scatters the electron, and the interlayer el-ph process, where the scattering occurs between states in the Dirac cones of adjacent graphene layers. [Eliel et al., Nature Comm. 9, 1221 (2018)]. I will then present a multiple excitation Raman study in a single atomic layer of MoS2, which is a semiconducting 2D material, where we could evidence electron scattering processes by acoustic phonons between different valleys in the electronic structure [Carvalho et al. Nature Comm. 8, 14670 (2017)] [Preview Abstract] |
Friday, October 22, 2021 11:12AM - 11:24AM |
J04.00003: $Z_2$ Topology and Edge States of Twisted Bilayer Graphene Qiyue Wang, Chao Ma, Fengnian Xia, Fan Zhang Recently twisted bilayer graphene(t-BLG) emerges as a new strongly correlated physical platform near a magic twist angle, which hosts many exciting phenomena such as the Mott-like insulating phases, unconventional superconducting behavior and emergent ferromagnetism. Besides the apparent significance of band flatness, band topology may be another critical element in strongly correlated twistronics yet receives much less attention. While an unusual symmetry of t-BLG trivializes Berry curvature, we elucidate that two high-dimensional $Z_2$ invariants in the Teo-Kane Altland-Zirnbauer table characterize the topology of the moir\'{e} Dirac bands, supported by a systematic nonlocal transport study. The moir\'{e} band topology of t-BLG manifests itself as two pronounced nonlocal responses in the electron and hole superlattice gaps. Moreover, the nonlocal responses are robust to the interlayer electric field, twist angle, and edge termination, exhibiting a universal scaling law. [Preview Abstract] |
Friday, October 22, 2021 11:24AM - 11:36AM |
J04.00004: Relationship between the lateral works of adhesion and the Young-Dupre equation. Rafael de la Madrid, Huy Luong, Jacob Zumwalt The Young-Dupre work of adhesion quantifies the energy necessary to detach a liquid drop from a solid substrate. In this talk, we will calculate the energy necessary to contract/expand/slide the contact area between a drop and a solid by contracting/expanding/sliding the triple line, and we will compare the resulting works with the Young-Dupre work of adhesion. [Preview Abstract] |
Friday, October 22, 2021 11:36AM - 11:48AM |
J04.00005: Electron-phonon and phonon-phonon interactions in low dimensional carbon materials. Ioannis Chatzakis, Sachin Sharma, Edward Sanchez ~~~~Low-dimensional (e.g. atomically thin) materials continue to gain prominence in applications ranging from electronics to photonics and alternative energy generation systems. Critical to efficiently developing these systems is the understanding of the fundamental processes related to the dynamics of charge carriers, phonons, and other excitations (i.e. excitons, polaritons). In this talk, I will focus on electron-phonon interactions in low dimensional carbon materials. Through these interactions the electrons lose all their excess energy above the band edge and become thermally equilibrated with the most strongly coupled optical phonon modes. Subsequently the optical phonons modes through unharmonic phonon-phonon scattering processes decay to lower-energy phonon modes. [Preview Abstract] |
Friday, October 22, 2021 11:48AM - 12:00PM |
J04.00006: Retaining Superconducting Phases Through Low Temperature Pressure Quenching Trevor Bontke, Liangzi Deng, Rabin Dahal, Yu Xie, Bin Gao, Xue Li, Ketao Yin, Melissa Gooch, Donald Rolston, Tong Chen, Zheng Wu, Yanming Ma, Pengcheng Dai, Ching-Wu Chu In the past 5 years the discovery of superhydride systems with critical temperatures (T$_{c}$s) that approach and exceed room temperature has pushed the field to new heights. Unfortunately, to achieve room temperature superconductivity (RTS) requires pressures in excess of 260 GPa. One of the greatest challenges remaining in field of superconductivity (SC) is retaining RTS while lowering or removing pressure. As a potential solution, we developed a low temperature pressure quenching technique which successfully retained SC phases in Bi, and FeSe and Cu$_{x}$Fe$_{1-x}$Se. Quenching at 77 K and 4.2 K from pressures up to 23.6 GPa we retained Bi phases with varying T$_{c}$s corresponding to Bi II, III, and V. Similarly, we retained SC phases with T$_{c}$s up to 38 K in FeSe and 27 K in Cu$_{x}$Fe$_{1-x}$Se. Furthermore, the retained SC phase of Cu$_{x}$Fe$_{1-x}$Se was shown to be stable for at least 7 days when kept at 77 K. Finally, stability testing of Bi revealed a robust SC phase with T$_{c}$s corresponding to Bi-III (T$_{c}$ 7.1 K) while displaying the transient nature of other retained SC phases of Bi. [Preview Abstract] |
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