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Title: Evidence for a topological excitonic insulator in InAs/GaSb bilayers

Abstract

Electron–hole pairing can occur in a dilute semimetal, transforming the system into an excitonic insulator state in which a gap spontaneously appears at the Fermi surface, analogous to a Bardeen–Cooper–Schrieffer (BCS) superconductor. Here, we report optical spectroscopic and electronic transport evidence for the formation of an excitonic insulator gap in an inverted InAs/GaSb quantum-well system at low temperatures and low electron–hole densities. Terahertz transmission spectra exhibit two absorption lines that are quantitatively consistent with predictions from the pair-breaking excitation dispersion calculated based on the BCS gap equation. Low-temperature electronic transport measurements reveal a gap of ~2 meV (or ~25 K) with a critical temperature of ~10 K in the bulk, together with quantized edge conductance, suggesting the occurrence of a topological excitonic insulator phase.

Authors:
 [1];  [1]; ORCiD logo [2];  [3];  [2];  [1];  [4]
  1. Rice Univ., Houston, TX (United States)
  2. Chinese Academy of Sciences (CAS), Beijing (China)
  3. Teledyne Scientific and Imaging, Thousand Oaks, CA (United States)
  4. Rice Univ., Houston, TX (United States); Peking Univ., Beijing (China)
Publication Date:
Research Org.:
Rice Univ., Houston, TX (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1499925
Grant/Contract Number:  
FG02-06ER46274
Resource Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE

Citation Formats

Du, Lingjie, Li, Xinwei, Lou, Wenkai, Sullivan, Gerard, Chang, Kai, Kono, Junichiro, and Du, Rui-Rui. Evidence for a topological excitonic insulator in InAs/GaSb bilayers. United States: N. p., 2017. Web. doi:10.1038/s41467-017-01988-1.
Du, Lingjie, Li, Xinwei, Lou, Wenkai, Sullivan, Gerard, Chang, Kai, Kono, Junichiro, & Du, Rui-Rui. Evidence for a topological excitonic insulator in InAs/GaSb bilayers. United States. doi:10.1038/s41467-017-01988-1.
Du, Lingjie, Li, Xinwei, Lou, Wenkai, Sullivan, Gerard, Chang, Kai, Kono, Junichiro, and Du, Rui-Rui. Thu . "Evidence for a topological excitonic insulator in InAs/GaSb bilayers". United States. doi:10.1038/s41467-017-01988-1. https://www.osti.gov/servlets/purl/1499925.
@article{osti_1499925,
title = {Evidence for a topological excitonic insulator in InAs/GaSb bilayers},
author = {Du, Lingjie and Li, Xinwei and Lou, Wenkai and Sullivan, Gerard and Chang, Kai and Kono, Junichiro and Du, Rui-Rui},
abstractNote = {Electron–hole pairing can occur in a dilute semimetal, transforming the system into an excitonic insulator state in which a gap spontaneously appears at the Fermi surface, analogous to a Bardeen–Cooper–Schrieffer (BCS) superconductor. Here, we report optical spectroscopic and electronic transport evidence for the formation of an excitonic insulator gap in an inverted InAs/GaSb quantum-well system at low temperatures and low electron–hole densities. Terahertz transmission spectra exhibit two absorption lines that are quantitatively consistent with predictions from the pair-breaking excitation dispersion calculated based on the BCS gap equation. Low-temperature electronic transport measurements reveal a gap of ~2 meV (or ~25 K) with a critical temperature of ~10 K in the bulk, together with quantized edge conductance, suggesting the occurrence of a topological excitonic insulator phase.},
doi = {10.1038/s41467-017-01988-1},
journal = {Nature Communications},
number = 1,
volume = 8,
place = {United States},
year = {2017},
month = {12}
}

Journal Article:
Free Publicly Available Full Text
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Cited by: 31 works
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Figures / Tables:

Fig. 1 Fig. 1 : Excitonic insulator in inverted InAs/GaSb quantum wells tuned by double gates. a Phase diagram for an electron–hole (e–h) system in the parameter space of temperature and e–h pair density. b Pink circle: an e–h plasma (or a semimetal). c Purple diamond: the excitonic insulator, where electrons andmore » holes are weakly bound, like Cooper pairs. d Red square: an exciton gas consisting of bosonic particles with a finite center-of-mass momentum. e Blue triangle: exciton Bose–Einstein condensate, where the exciton states are degenerate. In b–e, the blue dots represent electrons, the red points are holes, the dashed ellipses indicate the strong binding between electrons and holes, the dashed lines with arrows mean the weak binding between electrons and holes, and the single arrows show the center-of-mass movement of excitons. f Sketch of a device with front and back gates. The back-gate is used to fix $p$0, and sweeping the front-gate voltage allows us to find a resistance peak at the charge-neutral-point, $n$0 ~ $p$0. g Band structure of InAs/GaSb quantum wells calculated using the 8-band k·p method, for low $n$0« less

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    journal, October 2018

    • Riva, E.; Quadrelli, D. E.; Cazzulani, G.
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      Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.