Large quantum-spin-Hall gap in single-layer 1T′ WSe2

P. Chen (), Woei Wu Pai, Y.-H. Chan, W.-L. Sun, C.-Z. Xu, D.-S. Lin, M. Y. Chou, A.-V. Fedorov and T.-C. Chiang ()
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P. Chen: University of Illinois at Urbana-Champaign
Woei Wu Pai: National Taiwan University
Y.-H. Chan: Academia Sinica
W.-L. Sun: National Tsing Hua University
C.-Z. Xu: University of Illinois at Urbana-Champaign
D.-S. Lin: National Tsing Hua University
M. Y. Chou: National Taiwan University
A.-V. Fedorov: Lawrence Berkeley National Laboratory
T.-C. Chiang: University of Illinois at Urbana-Champaign

Nature Communications, 2018, vol. 9, issue 1, 1-7

Abstract: Abstract Two-dimensional (2D) topological insulators (TIs) are promising platforms for low-dissipation spintronic devices based on the quantum-spin-Hall (QSH) effect, but experimental realization of such systems with a large band gap suitable for room-temperature applications has proven difficult. Here, we report the successful growth on bilayer graphene of a quasi-freestanding WSe2 single layer with the 1T′ structure that does not exist in the bulk form of WSe2. Using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS), we observe a gap of 129 meV in the 1T′ layer and an in-gap edge state located near the layer boundary. The system′s 2D TI characters are confirmed by first-principles calculations. The observed gap diminishes with doping by Rb adsorption, ultimately leading to an insulator–semimetal transition. The discovery of this large-gap 2D TI with a tunable band gap opens up opportunities for developing advanced nanoscale systems and quantum devices.

Date: 2018
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DOI: 10.1038/s41467-018-04395-2

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