Quantum anomalous Hall effect in two-dimensional ferromagnetic Mn2XSe4 (X = Al, Ga, In)

As a topological phase with chiral edge states in the absence of a magnetic field, quantum anomalous Hall (QAH) insulators have become a booming topic in low-power-consumption electronic devices, and two-dimensional ferromagnetic compounds provide a platform for designing QAH insulators. Here, a family of ternary transition metal chalcogenide, Mn2XSe4 (X = Al, Ga, In) monolayers, are proposed to be stable QAH insulators with large QAH gaps (larger than 0.2 eV) combining the first-principles calculations and tight-binding model analysis. It is found that the Mn-dxy orbitals in the majority channel form a quadratic non-Dirac point near the Fermi level. Interestingly, a large bandgap is caused by including a spin–orbital coupling effect, and one chiral edge state connecting conduction and valence bands appears, forming a Chern insulator with C = 1. Moreover, the magnetic and topological properties of the Mn2XSe4 monolayers can be adjusted by biaxial strains. Our work suggests that the Mn2XSe4 monolayers can serve as candidates for exploring the QAH effect and spintronic devices.