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.

SUBMITTER: Du L 

PROVIDER: S-EPMC5719361 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature