Half-Dirac semimetals and the quantum anomalous Hall effect in Kagome Cd2N3 lattices.

Abstract

Half-Dirac semimetals (HDSs), which possess 100% spin-polarizations for Dirac materials, are highly desirable for exploring various topological phases of matter as low-dimensionality opens unprecedented opportunities for manipulating the quantum state of low-cost electronic nanodevices. The search for high-temperature HDSs is still a current hotspot and yet challenging experimentally. Herein based on first-principles calculations, we propose the realization of Half Dirac semimetals (HDS) in two-dimensional (2D) Kagome transition-metal nitride Cd2N3, which is robust against strain engineering. Monte Carlo simulations reveal that Cd2N3 possesses a Curie temperature reaching up to TC = 225 K, which is much higher than that of the reported monolayers CrI3 (TC = 45 K) and Cr2Ge2Te6 (TC = 20 K). The band crossings in Cd2N3 are gapped out by the spin–orbit coupling, which brings about the quantum anomalous Hall (QAH) effect with a sizeable band gap of Eg = 4.9 meV, characterized by the nonzero Chern number (C = 1) and chiral edge states. A tight-binding model is further used to clarify the origin of HDSs and nontrivial electronic properties. The results suggest monolayer transition-metal nitrides as a promising platform to explore fascinating physical phenomena associated with novel 2D emergent HDSs and QAH insulators toward realistic spintronics devices, thus stimulating experimental interest.