Heterobilayer with Ferroelectric Switching of Topological State.

The realization of multifunctional nanomaterials is both fundamentally intriguing and practically appealing to be used in nanoscale devices. Here, a heterobilayer consisting of realistic 2D-material components of matching lattice symmetry, that is, one being the β-phase antimonene β-Sb known for its strong spin-orbit coupling and ferroelectric In2Se3 monolayer, is designed and explored with first-principles density functional theory. The ferroelectric polarization of the In2Se3 layer induces distinctly different electronic properties in the bilayer. With polarization directed "inward", the bilayer is a trivial insulator with spatially-indirect band gap (potentially beneficial for photovoltaics). Surprisingly, when polarized "outward", the bilayer displays nontrivial topological state, Z2 = 1. This suggests that the external electric field can reversibly switch between these two states, inviting potential applications in future multifunctional devices.