Four allotropes of semiconducting layered arsenic that switch into a topological insulator via an electric field: Computational study

Abstract

We propose four different thermodynamically stable structural phases of arsenic monolayers based on ab initio density functional theory calculations, all of which undergo a topological phase transition on application of a perpendicular electric field. All four arsenic monolayer allotropes have a wide band gap, varying from 1.21 to 3.0 eV (based on GW calculations), and in general they undergo a metal-insulator quantum phase transition on application of uniaxial in-layer strain. Additionally, an increasing transverse electric field induces band inversion at the $\mathrm{\ensuremath{\Gamma}}$ point in all four monolayer allotropes, leading to a nontrivial topological phase (insulating for three allotropes and metallic for one allotrope), characterized by the switching of the ${Z}_{2}$ index from 0 (before band inversion) to 1 (after band inversion). The topological phase tuned by the transverse electric field should support spin-separated gapless edge states which should manifest in the quantum spin Hall effect.