Large-gap quantum anomalous Hall effect in monolayer halide perovskite

We theoretically propose a family of structurally stable monolayer halide perovskite A$_3$B$_2$C$_9$ (A=Rb, Cs; B=Pd, Pt; C=Cl, Br) with easy magnetization planes. These materials are all half-metals large spin gaps over 1~eV accompanying single Dirac point located at K point. When the spin-orbit coupling is switched on, we further show that Rb$_3$Pt$_2$Cl$_9$, Cs$_3$Pd$_2$Cl$_9$, and Cs$_3$Pt$_2$Cl$_9$ monolayers can open up band from 63 to 103 meV harbor quantum anomalous Hall effect Chern numbers $\mathcal{C}=\pm1$, whenever mirror symmetry broken by in-plane magnetization. The corresponding Berezinskii-Kosterlitz-Thouless transition temperatures 248~K. Our findings provide potentially realizable platform explore spintronics high temperatures.