Fe₃GeTe₂-based magnetic van der Waals heterostructures for valleytronics applications

The monolayer transition metal dichalcogenides (TMDs) are promising for valleytronics applications, due to their large spin-orbit coupling and loss of inversion symmetry. So far, numerous works have shown the optical control of the valley degree of freedom of TMDs. But to electrical control of this degree of freedom remains challenging. Here, we demonstrate the novel van der Waals heterostructures that incorporate a monolayer WSe₂ integrated with an ultrathin Fe₃GeTe₂ (FGT) magnetic contact. The exploited magnetic contact could inject spin-polarized carriers into a monolayer TMD, leading to valley-dependent polarization, as confirmed by our helicity-dependent electroluminescence and reflective magnetic circular dichroism measurements. In addition, our measurements indicate that injecting spin-polarized holes from FGT into WSe₂ can more effectively lead to valley polarization, compared with injecting spin-polarized electrons from FGT. Based on our density functional theory calculations, we reveal such phenomenon is related to the unique electronic structure of FGT.