Dirac-semimetal phase diagram of two-dimensional black phosphorus

TL;DR

This paper constructs a comprehensive phase diagram for the Dirac-semimetal phase in black phosphorus, revealing its topological nature and providing insights for designing topological materials and devices.

Contribution

It offers a unified understanding of the band-gap closing mechanisms and the topological characteristics of the Dirac-semimetal phase in layered black phosphorus.

Findings

The Dirac-semimetal phase is topologically connected across different perturbations.

The phase diagram maps pressure, strain, and electric field effects.

The approach can be applied to other anisotropic layered materials.

Abstract

Black phosphorus (BP), a layered van der Waals material, reportedly has a band gap sensitive to external perturbations and manifests a Dirac-semimetal phase when its band gap is closed. Previous studies were focused on effects of each perturbation, lacking a unified picture for the band-gap closing and the Dirac-semimetal phase. Here, using pseudospins from the glide-reflection symmetry, we study the electronic structures of mono- and bilayer BP and construct the phase diagram of the Dirac-semimetal phase in the parameter space related to pressure, strain, and electric field. We find that the Dirac-semimetal phase in BP layers is singly connected in the phase diagram, indicating the phase is topologically identical regardless of the gap-closing mechanism. Our findings can be generalized to the Dirac semimetal phase in anisotropic layered materials and can play a guiding role in search for a new class of topological materials and devices.