Controlling the spin and valley degeneracy splitting in monolayer MnPSe by atom doping.

Monolayer manganese chalcogenophosphates MnPSe possess a pair of non-degenerate energy valleys in the vicinities of the vertices of the hexagonal Brillouin zone, which exhibit fascinating optical valley polarization. However, the spin is still degenerate due to antiferromagnetic coupling between Mn ions. In this paper we propose a strategy to realize simultaneously the spin and valley degeneracy splitting by the doping-induced Zeeman effect in monolayer MnPSe. Using first-principles calculations we demonstrate that in Zn-doped monolayer MnPSe a valley splitting of larger than 20 meV and a spin splitting of larger than 100 meV can be achieved simultaneously. The doping-induced spin and valley splitting is attractive for spintronics and valleytronics as it creates differences in various energy scales between valleys and between spins, which will facilitate the access and manipulation of the valley and spin degrees of freedom by electrical gating in addition to optical pumping.