Ti3O5 monolayer: Tunable quantum anomalous Hall insulator

The quantum anomalous Hall (QAH) effect has attracted significant attention due to its potential applications in low-power-consumption spintronic devices. In this study, we performed density functional theory calculations to investigate the stability, electronic, and topological properties of ${\mathrm{Ti}}_{3}{\mathrm{O}}_{5}$ monolayer. Our results demonstrate that ${\mathrm{Ti}}_{3}{\mathrm{O}}_{5}$ monolayer is thermally and dynamically stable. In the absence of spin-orbit coupling (SOC), the monolayer exhibits spin-polarized Weyl semimetal behavior and the Weyl points are protected by the vertical mirror symmetry. Specifically, the Weyl points can be preserved when the magnetization direction is parallel to xoy plane. By altering the magnetization direction out of plane, the Weyl points are opened and the system is transformed into the QAH phase $(|C|=1)$. To validate our findings, we constructed a 12-band tight-binding model based on first-principles calculations, which successfully reproduces the QAH state by incorporating exchange coupling and the SOC term. Furthermore, it is observed that a transition from ferromagnetic QAH insulator to antiferromagnetic semiconductor occurs when biaxial compressive strain is applied. These results open up exciting possibilities for the realization of two-dimensional Weyl semimetals and the QAH effect in a single material, which has significant applications for the fields of spintronics and topological microelectronics.