Quantum anomalous Hall and valley quantum anomalous Hall effects in two-dimensional d0 orbital XY monolayers

We propose a new family of the ${d}^{0}$ orbital $XY$ ($X$ = K, Rb, Cs; $Y$ = N, P, As, Sb, Bi) monolayers with abundant and novel topology and valley properties. The KN, RbN, RbP, RbAs, CsP, CsAs, and CsSb monolayers possess remarkable quantum anomalous Hall effect (QAHE). The CsSb monolayer also exhibits extraordinary valley QAHE with giant splitting. Moreover, the topological properties of $XY$ monolayers can be efficiently tuned by the in-plane strain, owing to the strain-induced band inversion between the ${p}_{x,y}$ and ${p}_{z}$ orbitals. Our findings suggest that the ${d}^{0}$ orbital $XY$ monolayers can be good candidates for promising applications in the spintronics and multifunctional topological-based devices.