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Large quantum-spin-Hall gap in single-layer 1T' WSe2.

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.

SUBMITTER: Chen P 

PROVIDER: S-EPMC5962594 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Large quantum-spin-Hall gap in single-layer 1T' WSe<sub>2</sub>.

Chen P P   Pai Woei Wu WW   Chan Y-H YH   Sun W-L WL   Xu C-Z CZ   Lin D-S DS   Chou M Y MY   Fedorov A-V AV   Chiang T-C TC  

Nature communications 20180521 1

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 WSe<sub>2</sub> single layer with the 1T' structure that does not exist in the bulk form of WSe<sub>2</sub>. Using angle-resolve  ...[more]

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