Valley polarization in monolayer CrX2 (X = S, Se) with magnetically doping and proximity coupling

Manipulating the valley degree of freedom as an information carrier has been a focused topic for both fundamental and applied research. Here, using first-principles calculations, we report the identification of monolayer CrX _2 (X = S, Se) as a novel two-dimensional valleytronic crystal. It shows large valley spin splitting in the valence band, attractive for the integration of valleytronics and spintronics. More importantly, through proximity coupling with monolayer CrCl _3 , the valley polarization in monolayer CrX _2 is achieved, which can be further engineered by stacking patterns. Also, the valley polarization in monolayer CrX _2 can be obtained via magnetically doping V and Mn. Specially for V-doped monolayer CrSe _2 , there are no impurity states in the band gap, beneficial for its practical applications. Our works thus provide not only exceptional two-dimensional valleytronic crystals but also promising ways for realizing valley polarizations in them.