Du, LingjieLi, XinweiLou, WenkaiSullivan, GerardChang, KaiKono, JunichiroDu, Rui-Rui2018-06-272018-06-272017Du, Lingjie, Li, Xinwei, Lou, Wenkai, et al.. "Evidence for a topological excitonic insulator in InAs/GaSb bilayers." <i>Nature Communications,</i> 8, (2017) Springer Nature: https://doi.org/10.1038/s41467-017-01988-1.https://hdl.handle.net/1911/102289Electron-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.engThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/ licenses/by/4.0/.Journal articles41467-017-01988-1https://doi.org/10.1038/s41467-017-01988-1