Films based on group IV–V–VI elements for the design of a large-gap quantum spin Hall insulator with tunable Rashba splitting
Abstract
Rashba spin–orbit coupling (SOC) in topological insulators (TIs) has recently attracted significant interest due to its potential applications in spintronics. However, to date, the coexistence of a giant Rashba SOC and band topology has rarely been investigated in two-dimensional (2D) films. Herein, we applied first-principles calculations to design a family of large-gap 2D topological insulators composed of hexagonal Bi and PbX (X = F, Cl, Br, and I) dimers. The nontrivial topology, induced via a pxy–pz band inversion, was confirmed by the Z2 index and helical edge states. Note that the Rashba splitting energy in these films reaches 81 meV, which is further tunable over a wide range of strains (−2–14%). Considering the robustness of the band topology on a h-BN substrate, this study provides a route for designing topological spintronic devices based on 2D films consisting of group IV–V–VI elements.