Evidence for a topological excitonic insulator in InAs/GaSb bilayers

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.

Type

Journal article

Citation

Du, Lingjie, Li, Xinwei, Lou, Wenkai, et al.. "Evidence for a topological excitonic insulator in InAs/GaSb bilayers." Nature Communications, 8, (2017) Springer Nature: https://doi.org/10.1038/s41467-017-01988-1.

Published Version

https://doi.org/10.1038/s41467-017-01988-1

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