Dumbbell Stanane: A large-gap quantum spin Hall insulator

Quantum spin Hall (QSH) effect is quite promising for applications in spintronics and quantum computations, but presently can only be achieved at ultralow temperature. Searching for large-gap QSH insulators is the key to increase the operating temperature. Using first-principles calculations, we demonstrate that the stable hydrogenated stanene with a dumbbell-like structure (DB stanane) has large topological nontrivial band gaps of 312 meV (gamma point) and 160 meV for bulk characterized by a topological invariant of Z2=1, due to the s-pxy band inversion. Helical gapless edge states appear in the nanoribbon structures with high Fermi velocity comparable to that of graphene. The nontrivial topological states are robust against the substrate effects. The realization of this material is a feasible solution for applications of QSH effect at room temperature and beneficial to the fabrication of high-speed spintronics devices.