Manipulation of valley splitting for the WSe2/NiCl2 heterostructure by adjusting the interlayer spacing and constructing a NiCl2/WSe2/NiCl2 heterojunction

The electronic band structure and valley splitting of the WSe _2 /NiCl _2 heterostructure have been investigated by density functional theory and Berry curvature calculations. We demonstrate that the valley polarization of monolayer WSe _2 is induced due to the magnetic proximity effect caused by the single layer of ferromagnetic NiCl _2 . The magnitude of valley splitting depends on the stacking configurations of WSe _2 /NiCl _2 , and the maximum value of valley splitting reaches −11.87 meV. Large valley splitting can be achieved by adjusting the layer spacing and constructing a NiCl _2 /WSe _2 /NiCl _2 heterojunction with Ni spins arranged in parallel between two NiCl _2 sheets. The valley-contrasting Berry curvature between the K and K ′ valleys suggests that the WSe _2 /NiCl _2 -based heterostructure could potentially be used as a valleytronic device to realize the valley-polarized anomalous Hall effect as both spin and valley filter.