Electric-field-induced Z2 topological phase transition in strained single bilayer Bi (111)

For controlling critical electric fields of the topological phase transition in a single bilayer Bi(111), we investigated topological phases in a strained system through first-principles calculations. We found a quadratic band touching semimetallic state at tensile strain epsilon = 0.5%. Around this strain, the topological phase can be switched to a trivial insulator by an infinitesimal electric field. The momentum positions at which Dirac cones appear in the electric-field-induced topological phase transition changed for the strain epsilon > 0.5% and epsilon < 0.5%. Our results indicate that this topological phase transition could be applied to novel spintronic devices. (C) 2019 The Japan Society of Applied Physics