Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session W54: Topological Devices and Nanostructures |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Jose Rodriguez, University of California, Los Angeles Room: Mile High Ballroom 2A |
Friday, March 6, 2020 8:00AM - 8:12AM |
W54.00001: Robust axion insulator and Chern insulator phases in a two-dimensional antiferromagnetic topological insulator Chang Liu, Yongchao Wang, Hao Li, Yang Wu, Yaoxin Li, Jiaheng Li, Ke He, Yong Xu, Jinsong Zhang, Yayu Wang Topology, magnetism, and two-dimensional materials are among the most actively-pursued fields in physics and material science. Here, we investigate the quantum transport behaviors of exfoliated MnBi2Te4, an antiferromagnetic topological insulator that hosts all three properties simultaneously. In the six septuple-layer crystal, we observe robust axion insulator state in zero magnetic field, over a wide field range, and at relatively high temperatures. A moderate magnetic field drives it into the Chern insulator state through a topological quantum phase transition. These results pave the road for realizing the topological magnetoelectric effect and axion electrodynamics in condensed matter systems. |
Friday, March 6, 2020 8:12AM - 8:24AM |
W54.00002: Gate field effects on the topological insulator BiSbTeSe2 interface Shuanglong Liu, Yang Xu, Yun-Peng Wang, Yong Chen, James Nathan Fry, Hai-ping Cheng Inspired by experimental efforts, we study interfacial processes between two slabs of BiSbTeSe2 (BSTS) via first principles calculations. Topological surface states are absent for the BSTS interface at its equilibrium separation, but our calculations show that they appear if the inter-slab distance is greater than 6 Å. More importantly, we find that topological interface states can be preserved by inserting two or more layers of hexagonal boron nitride between the two BSTS slabs. Using a first-principles based method that allows us to simulate a back gate, we observe that at low bias the extra charge induced by a gate voltage resides on the surface that is closest to the gate electrode, leaving the interface almost undoped. This explains the origin of the observed insensitivity of transport properties to back voltage at low bias. Our study resolves a few questions raised in experiment, which does not yet offer a clear correlation between microscopic physics and transport data. |
Friday, March 6, 2020 8:24AM - 8:36AM |
W54.00003: Controlling Strain Gradients in Weyl Semimetals Carsten Putzke, Jonas Diaz-Gomez, Roni Ilan, Dmitry I. Pikulin, Adolfo G Grushin, Nityan Nair, Chandra Shekhar, Horst Borrmann, Claudia Felser, James Analytis, Philip Moll Exposing Weyl semimetals to an external magnetic field leads to the quasiparticle chirality, which has attracted much attention over the past years. The magnetic field causes a shift in the node position and opens a new transport channel. The application of strong magnetic fields for future technological use of this phenomenon is technically impractical. An alternative path has been proposed theoretically1. By using strain gradients in Weyl semi-metals it is possible to tune the position of the nodes in a spatially inhomogeneous manner, causing a similar effect as the application of a magnetic field, hence termed pseudo-magnetic field. In the Dirac semimetal Cd3As2 the application of the magnetic field leads to splitting into Weyl nodes with Fermi arcs only pointing along kz, making this a good test candidate. We will show how the new concept of pseudo-magnetic fields is applied to Cd3As2. Using focused ion beam micro structuring we have been able to fabricate samples of Cd3As2 that can be deformed elastically by bending. Studying the coherent electron path composed of two Fermi arcs on opposing surfaces has allowed us to test the proposed pseudo-magnetic fields and to give an upper limit for its strength. |
Friday, March 6, 2020 8:36AM - 8:48AM |
W54.00004: Spinful quantum dot coupled to the edge states of a topological insulator Parameshwar Pasnoori, Natan Andrei, Colin Rylands Coupling a local quantum impurity to an interacting one dimensional system leads to striking strongly correlated effects. Here we study a spinful quantum dot coupled to the edge states of a topological insulator modeled by an interacting helical Luttinger liquid. We solve the model exactly using Bethe Ansatz and study the ground state properties of the system including the occupation number of the impurity and its density of states. Explicit expressions for the impurity magnetic susceptibility is derived at zero temperature. |
Friday, March 6, 2020 8:48AM - 9:00AM |
W54.00005: Current-driven dynamics of spin textures on a surface of topological insulators Daichi Kurebayashi, Naoto Nagaosa The application of topological properties has attracted research interest to more efficiently manipulate magnetization. For instance, at the interface of the topological insulator and the ferromagnetic insulator, the electrical control of magnetic textures, magnetization switching induced by electric current, and spin-charge conversion have been intensely studied theoretically and experimentally. |
Friday, March 6, 2020 9:00AM - 9:12AM |
W54.00006: Nontrivial topology in ultrathin bismuth nanowires: An electronic transport study. Tito Huber, Albina Nikolaeva, Leonid Konopko In the past, bismuth was considered to be topologically trivial on the basis of theoretical study of band inversions and angle resolved photoemission spectroscopy. However, the topological properties of bismuth are the subject of renewed study because of the observations of high mobility exhibited by Bi nanowires (suggesting topological protection) as well as the proposal of higher-order topology. We studied the magnetoresistance (MR) in samples of ultrathin nanowires of bismuth, diameter ~50 nm, that exhibit high mobility (Huber et al, Scientific Reports 7,15569 (2017)). The MR exhibits peaks for a sequence of orientations of the magnetic field B, including a coherence peak for B//(111), that can be interpreted in terms of Yamaji magic angles . Magic angles are observed in layered conductors with an open, corrugated, Fermi surface. In contrast, bulk bismuth does not display magic angles since the Fermi surface consist of small ellipsoids and is closed. We will discuss our interpretation of the observations in terms of inter-Bi bilayer coupling and hinge states. |
Friday, March 6, 2020 9:12AM - 9:24AM |
W54.00007: Non-local Fermi level tuning of topological insultor Bi2-xSbxSe3 nanoplate devices Yasen Hou, Rui Xiao, Luke McClintock, Henry Travaglini, Dong Yu The spin-polarized topological surface states of a topological insulators (TIs) are attractive because of their potential applications in spintronics. A critical challenge of accessing the surface states is to reliably tune the chemical potential with respect to the bulk bands and Dirac point. Here we report non-local Fermi level tuning in Bi2-xSbxSe3 nanoplate devices. We found that applying a local electric field on a Bi2-xSbxSe3 nanoplate device induces a Fermi level shift hundreds of microns away. As temperature decreases to 77K, such a Fermi level shift is frozen, and the device stay in a different electronic state. Magnitude and direction of the Fermi level shift can be controlled by the applied electric field, which then tune the device conductance, field effect behavior and photo-generated carrier transport distance. The non-local Fermi level shift follows very well with a diffusion model and predicts a diffusion coefficient of 2x10-6cm2/S at room temperature. Potential candidates for the diffusing carriers include vacancies of selenium and charge traps. |
Friday, March 6, 2020 9:24AM - 9:36AM |
W54.00008: Quantum spin Hall quantum point contacts Christoph Fleckenstein Quantum spin Hall insulators (QSHIs) provide helical, time reversal protected edge modes. When strongly localized and thus considerably one-dimensional, these edge states may be described in terms of helical Luttinger liquids. In that respect, especially the formation of interaction induced gaps is particularly exciting. Although the formation of the underlying scattering terms might be demanding for isolated helical edges, the situation shifts when both edges of the QSHI are brought in proximity to each other. Then, the increased number of channels enables a variety of scattering terms, all of which relevant even for weak repulsive Coulomb interactions. Indeed, very recent transport experiments on QSHI quantum point contacts not only imply the existence of interactions at the helical edge, but also indicate the presence of two-particle scattering terms. This is especially interesting, since these terms, among proximity induced superconductivity, constitute one brick for the construction of parafermionic excitations in the same system. |
Friday, March 6, 2020 9:36AM - 9:48AM |
W54.00009: Giant and gate-tunable spin-galvanic effect in graphene-topological insulator van der Waals heterostructures at room temperature Dmitrii Khokhriakov, Md Anamul Hoque, Bogdan Karpiak, Saroj Dash Unique electronic spin textures in topological states of matter are promising for emerging spin-orbit driven memory and logic technologies. However, there are several challenges related to the enhancement of their performance, electrical gate-tunability, interference from trivial bulk states, and heterostructure interfaces. We address these challenges by integrating graphene [1] with a 3D topological insulator (TI) in a van der Waals heterostructure [2] to take advantage of their remarkable spintronic properties and engineer strong proximity-induced spin-charge conversion phenomena. In these heterostructures, we experimentally demonstrate a giant spin-galvanic effect at room temperature due to an efficient conversion of a nonequilibrium spin polarization into a transverse charge current [3]. Importantly, we show a strong gate-tunability of the spin-galvanic signal, tracing its origin to the proximity-induced Rashba-Edelstein effect. These findings open interesting opportunities for exploring exotic physical phenomena and new device functionalities governed by topological proximity effects. |
Friday, March 6, 2020 9:48AM - 10:00AM |
W54.00010: Topological Sliding Moiré Heterostructure Shizeng Lin, Ying Su We investigate the effect of sliding motion of layers in Moiré heterostructures on the electronic state. We show that the sliding Moiré heterostructure can generate nontrivial topology characterized by the first and second Chern number in the high dimensional manifold spanned by the physical dimensions and synthetic dimensions associated with the sliding displacement. The nontrivial topology implies a topological charge pumping caused by the sliding motion. We demonstrate the nontrivial topology and charge pumping explicitly in a one dimensional bi-chain model and the small-angle twisted bilayer graphene. Contrary to the conventional belief that the interlayer sliding in incommensurate Moiré Heterostructures does not affect the electronic structure, our results reveal that the sliding motion can generate nontrivial topology dynamically and hence cannot be neglected in the dynamical process. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700