@article{8ca900be67e94429b20c1331737b902e,
title = "Evidence for a monolayer excitonic insulator",
abstract = "The interplay between topology and correlations can generate a variety of quantum phases, many of which remain to be explored. Recent advances have identified monolayer WTe2 as a promising material for doing so in a highly tunable fashion. The ground state of this two-dimensional crystal can be electrostatically tuned from a quantum spin Hall insulator to a superconductor. However, much remains unknown about the gap-opening mechanism of the insulating state. Here we report evidence that the quantum spin Hall insulator is also an excitonic insulator, arising from the spontaneous formation of electron–hole bound states, namely excitons. We reveal the presence of an intrinsic insulating state at the charge neutrality point in clean samples and confirm the correlated nature of this charge-neutral insulator by tunnelling spectroscopy. We provide evidence against alternative scenarios of a band insulator or a localized insulator and support the existence of an excitonic insulator phase in the clean limit. These observations lay the foundation for understanding a new class of correlated insulators with nontrivial topology and identify monolayer WTe2 as a promising candidate for exploring quantum phases of ground-state excitons.",
author = "Yanyu Jia and Pengjie Wang and Chiu, {Cheng Li} and Zhida Song and Guo Yu and Berthold J{\"a}ck and Shiming Lei and Sebastian Klemenz and Cevallos, {F. Alexandre} and Michael Onyszczak and Nadezhda Fishchenko and Xiaomeng Liu and Gelareh Farahi and Fang Xie and Yuanfeng Xu and Kenji Watanabe and Takashi Taniguchi and Bernevig, {B. Andrei} and Cava, {Robert J.} and Schoop, {Leslie M.} and Ali Yazdani and Sanfeng Wu",
note = "Funding Information: lab was primarily supported by the Gordon and Betty Moore Foundation EPiQS initiative grants GBMF4530 and GBMF9469 and by the Department of Energy (DOE) BES grant DE-FG02-07ER46419. Other support for the experimental work by A.Y. was provided by NSF (DMR-1904442), ExxonMobil through the Andlinger Center for Energy and the Environment at Princeton, and the Princeton Catalysis Initiative. B.A.B. is supported by DOE grant no. DE-SC0016239, the Schmidt Fund for Innovative Research, Simons Investigator grant no. 404513 and the Packard Foundation for the numerical work. The analytical part was supported by NSF EAGER grant no. DMR-1643312, United States–Israel BSF grant no. 2018226, ONR grant no. N00014-20-1-2303 and the Princeton Global Network Funds. Additional support to B.A.B. was provided by the Gordon and Betty Moore Foundation through grant no. GBMF8685 towards the Princeton theory program. B.J. acknowledges funding through a postdoctoral fellowship of the Alexander-von-Humboldt Foundation. K.W. and T.T. acknowledge support from MEXT Element Strategy Initiative (Japan) grant no. JPMXP0112101001, JSPS KAKENHI grant no. JP20H00354 and the JST CREST (JPMJCR15F3). F.A.C. and R.J.C. acknowledge support from the ARO MURI on Topological Insulators (grant no. W911NF1210461). S.L, S.K. and L.M.S. acknowledge support from the Gordon and Betty Moore Foundation through grant no. GBMF9064 awarded to L.M.S. Publisher Copyright: {\textcopyright} 2021, The Author(s), under exclusive licence to Springer Nature Limited.",
year = "2022",
month = jan,
doi = "10.1038/s41567-021-01422-w",
language = "English (US)",
volume = "18",
pages = "87--93",
journal = "Nature Physics",
issn = "1745-2473",
publisher = "Nature Publishing Group",
number = "1",
}