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Title: Unexpected edge conduction in mercury telluride quantum wells under broken time-reversal symmetry

The realization of quantum spin Hall effect in HgTe quantum wells is considered a milestone in the discovery of topological insulators. Quantum spin Hall states are predicted to allow current flow at the edges of an insulating bulk, as demonstrated in various experiments. A key prediction yet to be experimentally verified is the breakdown of the edge conduction under broken time-reversal symmetry. Here we first establish a systematic framework for the magnetic field dependence of electrostatically gated quantum spin Hall devices. We then study edge conduction of an inverted quantum well device under broken time-reversal symmetry using microwave impedance microscopy, and compare our findings to a non-inverted device. At zero magnetic field, only the inverted device shows clear edge conduction in its local conductivity profile, consistent with theory. Surprisingly, the edge conduction persists up to 9 T with little change. Finally, this indicates physics beyond simple quantum spin Hall model, including material-specific properties and possibly many-body effects.
Authors:
 [1] ;  [1] ; ORCiD logo [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [1] ;  [1] ;  [1] ;  [1] ;  [3] ;  [3] ;  [3] ;  [3] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Stanford Univ., Stanford, CA (United States)
  2. Stanford Univ., Stanford, CA (United States); Univ. Wurzburg, Wurzburg (Germany)
  3. Univ. Wurzburg, Wurzburg (Germany)
  4. Stanford Univ., Stanford, CA (United States); Univ. of Texas, Austin, TX (United States)
Publication Date:
Grant/Contract Number:
AC02-76SF00515; PHY-0830228; DMR1305731; FP7-PEOPLE-2010-274769
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 6; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Stanford Univ., CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1260964

Ma, Eric Yue, Calvo, M. Reyes, Wang, Jing, Lian, Biao, Muhlbauer, Mathias, Brune, Christoph, Cui, Yong -Tao, Lai, Keji, Kundhikanjana, Worasom, Yang, Yongliang, Baenninger, Matthias, Konig, Markus, Ames, Christopher, Buhmann, Hartmut, Leubner, Philipp, Molenkamp, Laurens W., Zhang, Shou -Cheng, Goldhaber-Gordon, David, Kelly, Michael A., and Shen, Zhi -Xun. Unexpected edge conduction in mercury telluride quantum wells under broken time-reversal symmetry. United States: N. p., Web. doi:10.1038/ncomms8252.
Ma, Eric Yue, Calvo, M. Reyes, Wang, Jing, Lian, Biao, Muhlbauer, Mathias, Brune, Christoph, Cui, Yong -Tao, Lai, Keji, Kundhikanjana, Worasom, Yang, Yongliang, Baenninger, Matthias, Konig, Markus, Ames, Christopher, Buhmann, Hartmut, Leubner, Philipp, Molenkamp, Laurens W., Zhang, Shou -Cheng, Goldhaber-Gordon, David, Kelly, Michael A., & Shen, Zhi -Xun. Unexpected edge conduction in mercury telluride quantum wells under broken time-reversal symmetry. United States. doi:10.1038/ncomms8252.
Ma, Eric Yue, Calvo, M. Reyes, Wang, Jing, Lian, Biao, Muhlbauer, Mathias, Brune, Christoph, Cui, Yong -Tao, Lai, Keji, Kundhikanjana, Worasom, Yang, Yongliang, Baenninger, Matthias, Konig, Markus, Ames, Christopher, Buhmann, Hartmut, Leubner, Philipp, Molenkamp, Laurens W., Zhang, Shou -Cheng, Goldhaber-Gordon, David, Kelly, Michael A., and Shen, Zhi -Xun. 2015. "Unexpected edge conduction in mercury telluride quantum wells under broken time-reversal symmetry". United States. doi:10.1038/ncomms8252. https://www.osti.gov/servlets/purl/1260964.
@article{osti_1260964,
title = {Unexpected edge conduction in mercury telluride quantum wells under broken time-reversal symmetry},
author = {Ma, Eric Yue and Calvo, M. Reyes and Wang, Jing and Lian, Biao and Muhlbauer, Mathias and Brune, Christoph and Cui, Yong -Tao and Lai, Keji and Kundhikanjana, Worasom and Yang, Yongliang and Baenninger, Matthias and Konig, Markus and Ames, Christopher and Buhmann, Hartmut and Leubner, Philipp and Molenkamp, Laurens W. and Zhang, Shou -Cheng and Goldhaber-Gordon, David and Kelly, Michael A. and Shen, Zhi -Xun},
abstractNote = {The realization of quantum spin Hall effect in HgTe quantum wells is considered a milestone in the discovery of topological insulators. Quantum spin Hall states are predicted to allow current flow at the edges of an insulating bulk, as demonstrated in various experiments. A key prediction yet to be experimentally verified is the breakdown of the edge conduction under broken time-reversal symmetry. Here we first establish a systematic framework for the magnetic field dependence of electrostatically gated quantum spin Hall devices. We then study edge conduction of an inverted quantum well device under broken time-reversal symmetry using microwave impedance microscopy, and compare our findings to a non-inverted device. At zero magnetic field, only the inverted device shows clear edge conduction in its local conductivity profile, consistent with theory. Surprisingly, the edge conduction persists up to 9 T with little change. Finally, this indicates physics beyond simple quantum spin Hall model, including material-specific properties and possibly many-body effects.},
doi = {10.1038/ncomms8252},
journal = {Nature Communications},
number = ,
volume = 6,
place = {United States},
year = {2015},
month = {5}
}