Two-dimensional antiferromagnetic Dirac fermions in monolayer TaCoTe$_2$

TL;DR

This paper predicts and characterizes a new 2D antiferromagnetic Dirac material, monolayer TaCoTe$_2$, which hosts unique Dirac points that can be controlled by magnetic orientation, expanding the understanding of magnetic Dirac fermions.

Contribution

It introduces monolayer TaCoTe$_2$ as a stable 2D AFM Dirac material with tunable Dirac points, a novel finding in magnetic 2D materials.

Findings

Hosts a pair of AFM Dirac points at the Fermi level without SOC.

A small gap opens at Dirac points with SOC, and a new robust Dirac point appears.

The Dirac point location and type can be tuned by Ne9el vector orientation.

Abstract

Dirac point in two-dimensional (2D) materials has been a fascinating subject of research. Recently, it has been theoretically predicted that Dirac point may also be stabilized in 2D magnetic systems. However, it remains a challenge to identify concrete 2D materials which host such magnetic Dirac point. Here, based on first-principles calculations and theoretical analysis, we propose a stable 2D material, the monolayers TaCoTe$_2$, as an antiferromagnetic (AFM) 2D Dirac material. We show that it has an AFM ground state with an out-of-plane N\'{e}el vector. It hosts a pair of 2D AFM Dirac points on the Fermi level in the absence of spin-orbit coupling (SOC). When the SOC is considered, a small gap is opened at the original Dirac points. Meanwhile, another pair of Dirac points appear on the Brillouin zone boundary below the Fermi level, which are robust under SOC and have a type-II dispersion. Such a type-II AFM Dirac point has not been observed before. We further show that the location of this Dirac point as well as its dispersion type can be controlled by tuning the N\'{e}el vector orientation.