Four allotropes of semiconducting layered Arsenic which switch into a topological insulator via an electric field: A computational study

TL;DR

This computational study predicts four stable arsenic monolayer allotropes that can switch from semiconductors to topological insulators under an electric field, revealing potential for spintronic applications.

Contribution

It introduces four thermodynamically stable arsenic monolayer phases and demonstrates their topological phase transition induced by electric fields using ab-initio calculations.

Findings

All four allotropes have wide band gaps from 1.21 eV to 3.0 eV.

Electric field induces band-inversion leading to topological phases.

Topological phases support spin-separated gapless edge states.

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 the four arsenic monolayer allotropes have a wide band gap, varying from 1.21 eV 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 {\Gamma} point in all four monolayer allotropes, leading to a nontrivial topological phase (insulating for three and metallic for one allotrope), characterized by the switching of the Z2 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 quantum spin Hall effect.