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

Using first-principles calculations, we found the topological phase transition induced by electric fields in one-bilayer Bi(111). The bandgap decreased with increasing electric field strength, and it is closed at 2.1 V/{\AA}. For fields exceeding 2.1 V/{\AA}, the bandgap increased with increasing electric field strength, reaching 0.34 eV at 4.0 V/{\AA}. 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.