First-principles study of topological phase transition in two-dimensional bismuth and its alloys

Bulk and thin-film bismuth have attracted wide physical interests since they show the topological insulating phase and anomalous transport properties such as spin-to-charge conversion in Bi/Ag interfaces, originating from its electronic structure with strong spin-orbit coupling. Especially, to explore the possibility of new device applications, it is important to investigate the electric field effect on topological insulating phases in the bismuth. In the previous study, we reported that the one-bilayer Bi(111) shows electric field inducing topological phase transition at E > 2.1 V/Å[1].
In this study, to reduce critical electric fields for application in novel devices, we investigate the electric-field and strain dependence of band structure and Z₂ topological invariant on one-bilayer Bi(111) and Bi_1-xM_x (M =P, As, Sb) alloy by the first-principle calculation. We will present the phase diagram and discuss the origin of changes in critical electric fields by alloying.
[1] H. Sawahata, N. Yamaguchi, H. Kotaka, and F. Ishii, arXiv:1710.04812.