Topological Phase in Non-centrosymmetric Material NaSnBi

We predict that a non-centrosymmetric material NaSnBi locates in a three-dimensional non-trivial topological phase under ambient pressure based on first-principle calculations. By deriving the effective model around the Gamma point, we find that the topological phase transition is driven by a Rashba spin-orbital coupling through an odd number of pairs of band touch due to a small anisotropic gap caused by quintic dispersion terms. In contrast to conventional topological insulators, the spin texture of the surface Dirac cone is right-handed and the surface states are strikingly different for different surface terminations.