Dirac Fermions in Antiferromagnetic Semimetal

TL;DR

This paper demonstrates the existence of Dirac fermions in antiferromagnetic semimetals where time-reversal and inversion symmetries are broken but their combination is preserved, expanding the class of Dirac materials.

Contribution

It introduces a new class of Dirac semimetals in antiferromagnetic systems, specifically proposing CuMnAs as a candidate and analyzing its symmetry-protected Dirac points.

Findings

Dirac fermions can exist in antiferromagnetic materials with broken $ ext{T}$ and $ ext{P}$ but preserved $ ext{PT}$ symmetry.

CuMnAs is proposed as a candidate material hosting Dirac fermions.

Surface states and bulk dispersions are characterized by ab initio calculations.

Abstract

The analogues of elementary particles have been extensively searched for in condensed matter systems because of both scientific interests and technological applications. Recently massless Dirac fermions were found to emerge as low energy excitations in the materials named Dirac semimetals. All the currently known Dirac semimetals are nonmagnetic with both time-reversal symmetry $\mathcal{T}$ and inversion symmetry $\mathcal{P}$. Here we show that Dirac fermions can exist in one type of antiferromagnetic systems, where $\mathcal{T}$ and $\mathcal{P}$ are broken but their combination $\mathcal{PT}$ is respected. We propose orthorhombic antiferromagnet CuMnAs as a candidate, analyze the robustness of the Dirac points with symmetry protections, and demonstrate its distinctive bulk dispersions as well as the corresponding surface states by \emph{ab initio} calculations. Our results give a new route towards the realization of Dirac materials, and provide a possible platform to study the interplay of Dirac fermion physics and magnetism.