Strain tuned topological insulator and Rashba induced anisotropic momentum locked Dirac-cones in two-dimensional SeTe monolayer.

Rashba spin-orbit coupling (SOC) in Topological Insulator (TI) is very interesting phenomenon and has received extensive attention in two-dimensional (2D) materials. However, the coexistence of Rashba SOC and band topology, especially for materials with square lattice, is still lacking. Here, by using first-principles calculations, we propose for the first time SeTe monolayer as a 2D candidate with this novel properties. We find that square lattice exhibits anisotropic band dispersions near the Fermi level and Rashba effect related to large SOC and inversion asymmetry, which lead to Dirac semimetal state. Another prominent feature is that SeTe can turn into a topological state under a tensile strain of only 1%, characterized by the Z2 invariant and helical edge states. Our findings demonstrate that SeTe is a promising materials for novel electronic and spintronics applications.