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 GG02: V: Topological Semimetals and Insulators, Interactions and Beyond |
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Sponsoring Units: DCMP Chair: Joshuah Heath, Dartmouth College Room: Virtual Room 2 |
Monday, March 20, 2023 12:30PM - 12:42PM |
GG02.00001: Towards a unifying description of Andreev, Majorana, quasi-Majorana, and Shockley states Pasquale Marra, Angela Nigro Majorana bound states can be, in principle, realized in the nontrivial phase of proximized nanowires with strong spin-orbit coupling or magnetic atom chains deposited on a conventional superconductor. In these 1D systems, zero-energy Majorana edge modes localize at the domain walls between topologically distinct phases, similar to the case of Jackiw-Rebbi solitons, which are solutions of the Majorana-Dirac equation on an inhomogeneous background. On the other hand, topologically trivial Andreev states below the particle-hole gap, sometimes called quasi-Majorana states, can originate from disorder or spatial inhomogeneities. Distinguishing between Majorana and Andreev states is an ongoing challenge that generated intense debate in the scientific community. Indeed, there is a continuous crossover between topologically nontrivial Majorana and topologically trivial Andreev states induced by smooth inhomogeneities, and this crossover can occur without closing the bulk gap [1]. This Majorana/Andreev crossover is driven by field inhomogeneities with a length scale comparable to the nanowire length and larger than the Majorana localization length. Here, we describe nontrivial Majorana bound states, Andreev bound states induced by spatial inhomogeneities and disorder, Shockley states, and Jackiw-Rebbi solitons in a unifying framework, introducing a characteristic length scale that can unambiguously distinguish between different regimes [2]. |
Monday, March 20, 2023 12:42PM - 12:54PM |
GG02.00002: Fast quantum transfer mediated by topological domain walls Juan Zurita, Charles Creffield, Gloria Platero In recent years, the number of proposed quantum protocols which use the protected end states of topological insulators has increased steadily. One of the challenges that most of these protocols face is the exponential scaling of their duration with transfer distance. This increases the number of errors and makes the protocols impractical for long-range transmission of information. |
Monday, March 20, 2023 12:54PM - 1:06PM |
GG02.00003: Longitudinal magnetoconductance and the planar Hall conductance in inhomogeneous Weyl semimetals AZAZ AHMAD, Girish Sharma, Sumanta Tewari, Karthik Raman Elastic deformations (strain) couple to the electronic degrees of freedom in Weyl semimetals as an axial magnetic field (chiral gauge field), which in turn affects their impurity dominated diffusive transport. Here we study the longitudinal magnetoconductance (LMC) in the presence of strain, Weyl cone tilt, and finite intervalley scattering, taking into account the momentum dependence of the scattering processes (both internode and intranode), as well as charge conservation. We show that strain induced chiral gauge field results in `strong sign-reversal' of the LMC, which is characterized by the reversal of orientation of the magnetoconductance parabola with respect to the magnetic field. On the other hand, external magnetic field results in `strong sign-reversal', only for sufficiently strong intervalley scattering. When both external and chiral gauge fields are present, we observe both strong and weak sign-reversal, where in the case of weak sign-reversal, the rise and fall of magnetoconductivity depends on the direction of the magnetic field and/or the chiral gauge field, and is not correlated with the orientation of the LMC parabola. The combination of the two fields is shown to generate striking features in the LMC phase diagram as a function of various parameters such as tilt, strain, and intervalley scattering. We also study the effect of strain induced chiral gauge field on the planar Hall conductance and highlight its distinct features that can be probed experimentally |
Monday, March 20, 2023 1:06PM - 1:18PM |
GG02.00004: Weyl excitations and topological surface states via helicon-phonon mixing Dmitry K Efimkin, Sergey Syzranov Helicons are low-frequency almost transverse electromagnetic waves supported by electron gas in the presence of external magnetic field. In metals and doped semiconductors their anisotropic dispersion relation can be tuned to intersect with the dispersion curves for acoustic or optical phonons that favors the formation of hybrid helicon-phonon modes. Previously, interactions with longitudinal phonons have been routinely disregraded since they are small at low angles between helicon wavevector and magnetic filed direction and completely vanishes if they are aligned. In the present paper we reconsider the formation of helicon-phonon waves and argue that the corresponding intersections between dispersion curves for the hybrid modes are the topologically protected Weyl points. We discus their possible manifestations and demonstrate the presence of topologically protected arc states. |
Monday, March 20, 2023 1:18PM - 1:30PM |
GG02.00005: Symmetry indicators for many-body topological phases Axel Fünfhaus, Thilo Kopp, Roser Valenti It is well known that many topological phases can be indicated by the symmetry behavior of their band structure at high symmetry points, which culminated in the development of topological quantum chemistry. This approach becomes problematic once interactions are added, as this does not permit conserved particle occupation numbers in reciprocal space. We face this challenge by generalizing the canonical momentum for translation invariant many-body wave functions via twisted boundary conditions. This allows for a symmetry analysis of the ground state wave function in twisted boundary space. We apply this ansatz to detect topological phase transitions in interacting Chern insulators and fractional Chern insulators by means of symmetry indicators. |
Monday, March 20, 2023 1:30PM - 1:42PM |
GG02.00006: Trigonal warping effects on optical properties of anomalous Hall materials Jyesta M Adhidewata, Eddwi H Hasdeo, Ahmad Ridwan Tresna Nugraha, M. Shoufie Ukhtary, Bobby E Gunara The topological nature of topological insulators is related to the symmetries present in the material, for example, the quantum spin Hall effect can be observed in topological insulators with time-reversal symmetry, while broken time-reversal symmetry may give rise to the presence of anomalous quantum Hall effect (AHE). Here we consider the effects of broken rotational symmetry on the Dirac cone of an AHE material by adding trigonal warping terms to the Dirac Hamiltonian. By calculating the linear optical conductivity semi-analytically, we can show that the Hall conductivity from each Dirac cone is quantized with Chern number ±1. The ±1 Chern number is caused by the appearance of additional Dirac cones due to the trigonal warping terms. This results in drastic changes in the anomalous Hall and longitudinal conductivity. The trigonal warping terms also activate the higher-order Hall responses which do not exist in an R-symmetric conventional Dirac material. We found the presence of a non-zero second-order transversal current contribution from the shift current even in the absence of Berry curvature dipole. This shift current does not vanish due to contributions of opposite chiralities rendering it observable in time-reversal symmetric systems. |
Monday, March 20, 2023 1:42PM - 1:54PM |
GG02.00007: Topological Fermi Liquids in Multi-band Systems Yi Li, Grayson R Frazier, Junyi Zhang Monopole superconducting and density-wave orders have been proposed in topological semimetal systems when pairing occurs between Fermi surfaces with different Chern numbers. The resulting orders are distinguished from the familiar s-, p-, and d-wave pairing orders by a nonzero pair monopole charge and are described by monopole harmonics. We generalize the framework above to explore topological Fermi liquids in multi-band systems with topological Fermi surfaces and inter-band interactions. We investigate the monopole harmonic generalization of sound modes in higher partial wave channels and exotic collective modes. |
Monday, March 20, 2023 1:54PM - 2:06PM |
GG02.00008: STM studies of a Weyl semiconductor Maksim Litskevich, Shafayat Hossain, Yang Fu, Qi Zhang, Zi-Jia Cheng, Guoqing Chang, Yu-Xiao Jiang, Tyler A Cochran, Daniel Multer, Xian Yang, Hechang Lei, Zahid M Hasan Topological phases of matter are at the frontier of scientific research and have a potential to become a building block of future electronic devices. Using scanning tunneling microscopy (STM) we probe a Weyl semiconductor material and reveal defect-free atomically flat surfaces with an energy gap of We observe that the atomic surfaces separated by a monolayer step edge exhibit a switch of the intensity of the tunneling spectrum below and above the Fermi level and develop a gap difference of at 4.2 K, thus effectively realizing AB stacking sequence of atomic layers. Temperature dependent STM measurements on AB surfaces show spectroscopic contrast weakening and gap difference shrinkage with the increasing temperature. The results of our STM study indicate a surprising electronic AB stacking of layers, possibly linked to the presence of a phonon-induced instability in the material. |
Monday, March 20, 2023 2:06PM - 2:18PM |
GG02.00009: Raman scattering study of charge density wave order in the magnetic kagome metal FeGe Shangfei Wu, Xiaokun Teng, Lebing Chen, Jay Shah, Ethan T Ritz, Turan Birol, Pengcheng Dai, Girsh E Blumberg
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Monday, March 20, 2023 2:18PM - 2:30PM |
GG02.00010: Bipolaronic superconductivity with dispersive phonons Chao Zhang, Nikolay Prokof'ev We use the newly developed Monte Carlo method based on the path-integral formulation of the particle sector in combination with the real space diagrammatics of the phonon sector to study the effects of a finite dispersion of optical phonon mode on BEC of bipolarons in the bond model. For dispersionless phonons, this model was recently shown to give rise to small-size, light-mass bipolarons that undergo a superfluid transition at high values of Tc. For dispersive phonons,Tc stays relatively high over a significantly broader range of the coupling strength and even keeps increases in the deep adiabatic regime. This means more possibilities and less need for fine-tuning in the search for new materials with high superconducting temperatures. |
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