Quantum anomalous Hall effect in stable 1T-YN$_2$ monolayer with a large nontrivial band gap and high Chern number

Abstract

The quantum anomalous Hall (QAH) effect is a topologically nontrivial phase, characterized by a non-zero Chern number defined in the bulk and chiral edge states in the boundary. Using first-principles calculations, we demonstrate the presence of the QAH effect in 1T-YN$_2$ monolayer, which was recently predicted to be a Dirac half metal without spin-orbit coupling (SOC). We show that the inclusion of SOC opens up a large nontrivial band gap of nearly $0.1$ eV in the electronic band structure. This results in the nontrivial bulk topology which is confirmed by the calculation of Berry curvature, anomalous Hall conductance and the presence of chiral edge states. Remarkably, a high Chern number $C = 3$ is found, and there are three corresponding gapless chiral edge states emerging inside the bulk gap. Our results open a new avenue in searching for QAH insulators with high temperature and high Chern numbers, which can have nontrivial practical applications.