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Title: Tetragonal bismuth bilayer: A stable and robust quantum spin hall insulator

In this study, topological insulators (TIs) exhibit novel physics with great promise for new devices, but considerable challenges remain to identify TIs with high structural stability and large nontrivial band gap suitable for practical applications. Here we predict by first-principles calculations a two-dimensional (2D) TI, also known as a quantum spin Hall (QSH) insulator, in a tetragonal bismuth bilayer (TB-Bi) structure that is dynamically and thermally stable based on phonon calculations and finite-temperature molecular dynamics simulations. Density functional theory and tight-binding calculations reveal a band inversion among the Bi-p orbits driven by the strong intrinsic spin–orbit coupling, producing a large nontrivial band gap, which can be effectively tuned by moderate strains. The helical gapless edge states exhibit a linear dispersion with a high Fermi velocity comparable to that of graphene, and the QSH phase remains robust on a NaCl substrate. These remarkable properties place TB-Bi among the most promising 2D TIs for high-speed spintronic devices, and the present results provide insights into the intriguing QSH phenomenon in this new Bi structure and offer guidance for its implementation in potential applications.
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [4] ;  [5] ;  [5] ;  [6] ;  [2]
  1. Queensland Univ. of Technology, Brisbane (Australia); Univ. of New South Wales, Sydney, NSW (Australia)
  2. Univ. of New South Wales, Sydney, NSW (Australia)
  3. Jacobs Univ. Bremen, Bremen (Germany)
  4. Univ. of Bremen, Bremen (Germany)
  5. Queensland Univ. of Technology, Brisbane (Australia)
  6. Univ. of Nevada, Las Vegas, NV (United States)
Publication Date:
OSTI Identifier:
1332448
Grant/Contract Number:
NA0001982
Type:
Accepted Manuscript
Journal Name:
2D Materials
Additional Journal Information:
Journal Volume: 2; Journal Issue: 4; Journal ID: ISSN 2053-1583
Publisher:
IOP Publishing
Research Org:
Univ. of Nevada, Las Vegas, NV (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE tetragonal bismuth bilayer; topological insulator; density functional theory; helical gaplessedge states