  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.
