First-principles study of electric-field-induced topological phase transition in one-bilayer Bi(111)

Using first-principles calculations, we determined the topological phase transition induced by electric fields in one-bilayer Bi(111). The bandgap is decreased from 0.32 to 0 eV when the applied electric field reaches 2.1V/angstrom. Further increasing the applied electric field opens the bandgap, which reaches 0.34 eV at 4.0V/angstrom. We computed the Z(2) invariant that characterizes topological insulator phases. As results, one-bilayer Bi(111) showed a topological phase transition induced by the electric field, from the topological insulator phase to the trivial insulator phase through a Dirac semimetal. This topological phase transition could be applied to novel devices. (C) 2018 The Japan Society of Applied Physics