Evidence of high-temperature exciton condensation in a two-dimensional semimetal

Gao, Qiang; Chan, Yang-hao; Wang, Yuzhe; Zhang, Haotian; Jinxu, Pu; Cui, Shengtao; Yang, Yichen; Liu, Zhengtai; Shen, Dawei; Sun, Zhe; Jiang, Juan; Chiang, Tai C.; Chen, Peng

doi:10.1038/s41467-023-36667-x

Evidence of high-temperature exciton condensation in a two-dimensional semimetal

Journal Article · Tue Feb 21 23:00:00 EST 2023 · Nature Communications

DOI:https://doi.org/10.1038/s41467-023-36667-x· OSTI ID:2419201

Gao, Qiang ^[1]; Chan, Yang-hao ^[2]; Wang, Yuzhe ^[3]; Zhang, Haotian ^[4]; Jinxu, Pu ^[4]; Cui, Shengtao ^[3]; Yang, Yichen ^[5]; ^[5]; ^[6]; Sun, Zhe ^[3]; ^[3]; ^[7]; ^[4]

Shanghai Jiao Tong Univ. (China); Shanghai Jiao Tong University, Shanghai (China)
Academia Sinica, Taipei (Taiwan); National Center for Theoretical Sciences, Taipei (Taiwan)
Univ. of Science and Technology of China, Hefei (China)
Shanghai Jiao Tong Univ. (China)
Chinese Academy of Sciences (CAS), Shanghai (China). Shanghai Institute of Microsystem and Information Technology (SIMIT)
Univ. of Science and Technology of China, Hefei (China); Chinese Academy of Sciences (CAS), Shanghai (China). Shanghai Institute of Microsystem and Information Technology (SIMIT)
Univ. of Illinois at Urbana-Champaign, IL (United States)

Electrons and holes can spontaneously form excitons and condense in a semimetal or semiconductor, as predicted decades ago. This type of Bose condensation can happen at much higher temperatures in comparison with dilute atomic gases. Two-dimensional (2D) materials with reduced Coulomb screening around the Fermi level are promising for realizing such a system. Here we report a change in the band structure accompanied by a phase transition at about 180 K in single-layer ZrTe₂ based on angle-resolved photoemission spectroscopy (ARPES) measurements. Below the transition temperature, gap opening and development of an ultra-flat band top around the zone center are observed. This gap and the phase transition are rapidly suppressed with extra carrier densities introduced by adding more layers or dopants on the surface. The results suggest the formation of an excitonic insulating ground state in single-layer ZrTe₂, and the findings are rationalized by first-principles calculations and a self-consistent mean-field theory. Our study provides evidence for exciton condensation in a 2D semimetal and demonstrates strong dimensionality effects on the formation of intrinsic bound electron–hole pairs in solids.

View Accepted Manuscript (DOE)

Research Organization:: Univ. of Illinois at Urbana-Champaign, IL (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); Ministry of Science and Technology of China; Science and Technology Commission of Shanghai Municipality; National Natural Science Foundation of China (NSFC)

Grant/Contract Number:: FG02-07ER46383

OSTI ID:: 2419201

Journal Information:: Nature Communications, Journal Name: Nature Communications Journal Issue: 1 Vol. 14; ISSN 2041-1723

Publisher:: Nature Publishing GroupCopyright Statement

Country of Publication:: United States

Language:: English

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