Genuine Dirac Half‐Metals in Two‐Dimensions

Abstract

When spin‐orbit coupling (SOC) is absent, all proposed half‐metals with twofold degenerate nodal points at the K (or K′) point in 2D materials are classified as “Dirac half‐metals” owing to the way graphene is utilized in the earliest studies. Actually, each band crossing point at the K or K′ point is described by a 2D Weyl Hamiltonian with definite chirality; hence, it should be a Weyl point. To the best of its knowledge, there have not yet been any reports of a genuine (i.e., fourfold degenerate) 2D Dirac point half‐metal. In this work, using first‐principles calculations, it proposes for the first time that the 2D d0‐type ferromagnet Mg4N4 is a genuine 2D Dirac half‐metal candidate with a fourfold degenerate Dirac point at the S high‐symmetry point, intrinsic magnetism, a high Curie temperature, 100% spin polarization, topology robust under the SOC and uniaxial and biaxial strains, and spin‐polarized edge states. This work can serve as a starting point for future predictions of intrinsically magnetic materials with genuine 2D Dirac points, which will aid the frontier of topo‐spintronics research in 2D systems.