Hydrogenation-induced large-gap quantum-spin-Hall insulator states in a germanium–tin dumbbell structure

Abstract

The quantum spin Hall (QSH) effect in two-dimensional topological insulators (2D TIs) is promising for building nanoscaled devices with low energy consumption. The 2D TIs with a bulk band gap larger than the atomic thermal motion energy at room temperature (∼26 meV) are essential for achieving room-temperature QSH effects. We proved from first-principles that this goal may be reached in a hydrogenated germanium–tin (Sn₆Ge₄H₄) dumbbell (DB) structure, where spin–orbit coupling (SOC) opens a bulk band gap of 235 meV. The topological nontriviality is related to the band inversion of s–p_xy of Sn atoms induced by surface hydrogenation and can be characterized by a topological invariant of Z₂ = 1. This work offers a promising candidate material for achieving long-desired room-temperature QSH effects.