Visualization of an axion insulating state at the transition between 2 chiral quantum anomalous Hall states
Abstract
Quantumrelativistic materials often host electronic phenomena with exotic spatial distributions. In particular, quantum anomalous Hall (QAH) insulators feature topological boundary currents whose chirality is determined by the magnetization orientation. However, understanding the microscopic nature of edge vs. bulk currents has remained a challenge due to the emergence of multidomain states at the phase transitions. Here we use microwave impedance microscopy (MIM) to directly image chiral edge currents and phase transitions in a magnetic topological insulator. Our images reveal a dramatic change in the edge state structure and an unexpected microwave response at the topological phase transition between the Chern number $N=1$ and $N=1$ states, consistent with the emergence of an insulating $N=0$ state. The magnetic transition width is independent of film thickness, but the transition pattern is distinct in differently initiated field sweeps. This behavior suggests that the $N=0$ state has 2 surface states with Hall conductivities of $\frac{1}{2}{e}^{2}/h$ but with opposite signs.
 Authors:

 Stanford Univ., CA (United States)
 Univ. of California, Riverside, CA (United States)
 Univ. of Tokyo (Japan)
 RIKEN Center for Emergent Matter Science, Saitama (Japan)
 Leibniz Inst. for Solid State and Materials Research (IFW), Dresden (Germany)
 Stanford Univ., CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES)
 Univ. of Tokyo (Japan); RIKEN Center for Emergent Matter Science, Saitama (Japan)
 Publication Date:
 Research Org.:
 SLAC National Accelerator Lab., Menlo Park, CA (United States)
 Sponsoring Org.:
 USDOE
 OSTI Identifier:
 1546797
 Grant/Contract Number:
 AC0276SF00515; GBMF4546; DMR1305731
 Resource Type:
 Accepted Manuscript
 Journal Name:
 Proceedings of the National Academy of Sciences of the United States of America
 Additional Journal Information:
 Journal Volume: 116; Journal Issue: 29; Journal ID: ISSN 00278424
 Publisher:
 National Academy of Sciences, Washington, DC (United States)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Citation Formats
Allen, Monica, Cui, Yongtao, Yue Ma, Eric, Mogi, Masataka, Kawamura, Minoru, Fulga, Ion Cosma, GoldhaberGordon, David, Tokura, Yoshinori, and Shen, ZhiXun. Visualization of an axion insulating state at the transition between 2 chiral quantum anomalous Hall states. United States: N. p., 2019.
Web. doi:10.1073/pnas.1818255116.
Allen, Monica, Cui, Yongtao, Yue Ma, Eric, Mogi, Masataka, Kawamura, Minoru, Fulga, Ion Cosma, GoldhaberGordon, David, Tokura, Yoshinori, & Shen, ZhiXun. Visualization of an axion insulating state at the transition between 2 chiral quantum anomalous Hall states. United States. https://doi.org/10.1073/pnas.1818255116
Allen, Monica, Cui, Yongtao, Yue Ma, Eric, Mogi, Masataka, Kawamura, Minoru, Fulga, Ion Cosma, GoldhaberGordon, David, Tokura, Yoshinori, and Shen, ZhiXun. Tue .
"Visualization of an axion insulating state at the transition between 2 chiral quantum anomalous Hall states". United States. https://doi.org/10.1073/pnas.1818255116. https://www.osti.gov/servlets/purl/1546797.
@article{osti_1546797,
title = {Visualization of an axion insulating state at the transition between 2 chiral quantum anomalous Hall states},
author = {Allen, Monica and Cui, Yongtao and Yue Ma, Eric and Mogi, Masataka and Kawamura, Minoru and Fulga, Ion Cosma and GoldhaberGordon, David and Tokura, Yoshinori and Shen, ZhiXun},
abstractNote = {Quantumrelativistic materials often host electronic phenomena with exotic spatial distributions. In particular, quantum anomalous Hall (QAH) insulators feature topological boundary currents whose chirality is determined by the magnetization orientation. However, understanding the microscopic nature of edge vs. bulk currents has remained a challenge due to the emergence of multidomain states at the phase transitions. Here we use microwave impedance microscopy (MIM) to directly image chiral edge currents and phase transitions in a magnetic topological insulator. Our images reveal a dramatic change in the edge state structure and an unexpected microwave response at the topological phase transition between the Chern number N=1 and N=1 states, consistent with the emergence of an insulating N=0 state. The magnetic transition width is independent of film thickness, but the transition pattern is distinct in differently initiated field sweeps. This behavior suggests that the N=0 state has 2 surface states with Hall conductivities of12e2/h but with opposite signs.},
doi = {10.1073/pnas.1818255116},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 29,
volume = 116,
place = {United States},
year = {2019},
month = {7}
}
Web of Science
Figures / Tables:
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Figures / Tables found in this record: