Two-dimensional triangular-lattice Ti3Se3X2 (X = S, Te) monolayer: Stable quantum anomalous Hall insulator with high temperature and high Chern number

The quantum anomalous Hall (QAH) effect, which combines the topological and magnetic properties of two-dimensional (2D) materials, remains a major research interest to people. In this work, we explore the stability, magnetic, and topological properties of the 2D triangular lattice Janus monolayer Ti3Se3X2 (X = S, Te), using first-principles calculations. It is revealed that the electronic and magnetic properties of these materials are stable and do not change sensitively with changes in the lattice constants. In the absence of spin–orbit coupling (SOC), both monolayers exhibit ferromagnetic Weyl semimetallic properties. With SOC, both Ti3Se3S2 and Ti3Se3Te2 monoalyers exhibit intrinsic QAH insulators with a high Chern number of 2 and a high Curie temperature (Tc > 1000 K). Furthermore, a symmetry-guided tight-binding model is constructed to elucidate the topological origins, emphasizing the contributions of d orbitals from Ti atoms. Our findings suggest that monolayer Ti3Se3X2 (X = S, Te) compounds hold potential for applications in spintronics and quantum computing. Our results offer a promising avenue in searching for high performance QAH insulators.