Two-dimensional antiferromagnetic Dirac fermions in monolayer TaCoTe2

Dirac points in two-dimensional (2D) materials have been a fascinating subject of research. Recently, it has been theoretically predicted that Dirac points may also be stabilized in 2D magnetic systems. However, it remains a challenge to identify concrete 2D materials which host such magnetic Dirac points. Here, based on first-principles calculations and theoretical analysis, we propose a stable 2D material, the monolayer TaCoTe2, as an antiferromagnetic (AFM) 2D Dirac material. We show that it has an AFM ground state with an out-of-plane Néel 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 Néel vector orientation.