Pressure-induced topological insulator in NaBaBi with right-handed surface spin texture

Starting from the three-dimensional Dirac semimetal in Na3Bi, we found a topological insulator (TI) in the known compound of NaBaBi by extra pressure. The TI of NaBaBi can be viewed as the distorted version of Na3Bi with breaking inversion symmetry. When the exchange-correlation energy is considered in generalized gradient approximation (GGA), the TI phase has a band inversion between the Bi-p and Na-s orbitals. Since GGA often overestimates the band inversion, we also performed more accurate calculations by using hybrid functional theory (HSE). From HSE calculations we found that NaBaBi exhibits as a trivial insulator at zero pressure, and the other TI phase with p-d inversion can be achieved by pressure. Though both of two TI phases have Dirac-cone-type surface states, they have opposite spin textures. In the upper cone, a lefthanded spin texture exists for the s-p inverted phase (similar to a common TI, e.g., Bi2Se3), whereas a righthanded spin texture appears for the p-d inverted phase. This work presents a prototype model of a TI exhibits righthanded spin texture.