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; T-C Chiang

doi:10.1038/s41467-018-04395-2

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

Nat Commun. 2018 May 21;9(1):2003. doi: 10.1038/s41467-018-04395-2.

Authors

P Chen^{1

2

3}, Woei Wu Pai^{4

5

6}, Y-H Chan⁷, W-L Sun⁸, C-Z Xu^{9

10}, D-S Lin⁸, M Y Chou^{5

6

11}, A-V Fedorov¹², T-C Chiang^{13

14

15}

Affiliations

¹ Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL, 61801-3080, USA. pchen229@illinois.edu.
² Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Avenue, Urbana, IL, 61801-2902, USA. pchen229@illinois.edu.
³ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. pchen229@illinois.edu.
⁴ Center for Condensed Matter Sciences, National Taiwan University, Taipei, 10617, Taiwan.
⁵ Department of Physics, National Taiwan University, Taipei, 10617, Taiwan.
⁶ Center of Atomic Initiative for New Materials, National Taiwan University, Taipei, 6 10617, Taiwan.
⁷ Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan.
⁸ Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan.
⁹ Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL, 61801-3080, USA.
¹⁰ Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Avenue, Urbana, IL, 61801-2902, USA.
¹¹ School of Physics, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
¹² Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
¹³ Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL, 61801-3080, USA. tcchiang@illinois.edu.
¹⁴ Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Avenue, Urbana, IL, 61801-2902, USA. tcchiang@illinois.edu.
¹⁵ Department of Physics, National Taiwan University, Taipei, 10617, Taiwan. tcchiang@illinois.edu.

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.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.