Monolayer Ru(OLi)<sub>2</sub> as an Ideal Room-Temperature\nFerrovalley Semiconductor with Intrinsic Out-of-Plane Ferromagnetism

Achieving sizable valley polarization in room-temperature\nferrovalley\nsemiconductors with out-of-plane magnetization is of great significance\nfor fundamental physics and information technology. Using ab initio\ncalculations and Monte Carlo simulations, we identify the freestanding\nRu(OLi)<sub>2</sub> monolayer as a scarce Ising-type semiconducting\nferromagnet with an ultrahigh Curie temperature of 1121 K and a considerable\nperpendicular magnetic anisotropy energy of 1212 μeV per unit\ncell. Due to its out-of-plane ferromagnetism and spin–orbital\ncoupling effect, the inversion-symmetry-broken Ru(OLi)<sub>2</sub> monolayer holds a spontaneous ultraclean valley polarization up\nto 220 meV in the top valence band. Also, we validate such a significant\nvalley polarization by the perturbation theory from the orbital projection\nband structure. Local direct bandgaps at two inequivalent valley states\nrender selective excitation of spin and valley-coupled carriers realizable\nthrough optical fields of different visible frequencies. The valley-contrasting\nBerry curvature facilitates the observation of an anomalous valley\nHall effect in the experimentally feasible hole-doped regime. These\nexceptional merits, along with their intrinsic robustness against\na moderate range of equibiaxial strains, shed light on the bright\napplication prospect of the synthesizable Ru(OLi)<sub>2</sub> monolayer\nfor valley-based spintronic and optoelectronic devices at room temperature.