Possibility of realizing quantum spin Hall effect at room temperature in stanene/Al2O3(0001)

Two-dimensional quantum spin Hall (QSH) insulators with reasonably wide band gaps are imperative for the development of various innovative technologies. Through systematic density functional calculations and tight-binding simulations, we found that stanene on an alpha-alumina surface may possess a sizeable topologically nontrivial band gap (similar to 0.25 eV) at the Gamma point. Furthermore, stanene is atomically bonded to but electronically decoupled from the substrate, providing high structural stability and isolated QSH states to a large extent. The underlying physical mechanism is rather general, and this finding may lead to the opening of a new vista for the exploration of QSH insulators for room temperature device applications.