Electric Field Induced Topological Phase Transition in Two-Dimensional Few-layer Black Phosphorus

TL;DR

This paper predicts that applying an electric field to few-layer black phosphorus can induce a topological phase transition, potentially enabling new spintronic devices and topological transistors.

Contribution

It demonstrates, through first-principles calculations, that electric fields can continuously tune black phosphorus from a normal insulator to a topological insulator and metal.

Findings

Electric field induces topological phase transition in black phosphorus.

Potential for electric field-controlled topological transistors.

Prediction of spin-separated, gapless edge states.

Abstract

Phosphorene is a novel two-dimensional material that can be isolated through mechanical exfoliation from layered black phosphorus, but unlike graphene and silicene, monolayer phosphorene has a large band gap. It was thus unsuspected to exhibit band inversion and the ensuing topological insulator behavior. It has recently attracted interest because of its proposed application as field effect transistors. Using first-principles calculations with applied perpendicular electric field F we predict a continuous transition from the normal insulator to a topological insulator and eventually to a metal as a function of F. The continuous tuning of topological behavior with electric field would lead to spin-separated, gapless edge states, i.e., quantum spins Hall effect. This finding opens the possibility of converting normal insulating materials into topological ones via electric field, and making a multi-functional field effect topological transistor that could manipulate simultaneously both spins and charge carrier.