Strain Tunable Quantum Spin Hall Insulating Phase in Halogen‐Decorated Double‐Layer Stanene

Abstract

Group IV graphene analogues such as stanene, plumbene, etc. have drawn attention because of their large spin–orbit coupling and thus being promising candidates for topological insulator. However, fabrication of these ultrathin monolayers is a daunting task. To reduce the difficulties of the fabrication of 2D topological insulators, bilayer materials with sizable nontrivial bandgaps can be a viable option. Chemically decorated bilayer stanene is a novel structure which has not been studied before. Herein, the topological characteristics of halogen‐decorated bilayer of stanene are studied and their topological nontriviality is confirmed by calculating the Z2 invariant. As the topological nontriviality can be preserved for these bilayers, these materials will have advantages over their monolayer counterparts in terms of fabrication difficulties. Halogen‐decorated stanene bilayers (except Br) are topologically nontrivial and their nontrivial nature is tunable by external strain. Hybrid functional (HSE06) has been employed to calculate the band structures of the materials at various strains. Also, the band structures of their zigzag nanoribbons have been analyzed. Lastly, the formation energy, quantum molecular dynamics, and phonon dispersion confirm their electronic and structural stability. The proposed material may speed up the fabrication of 2D topological insulators aiming future spintronic and high‐speed electronic devices.