Magnetic proximity effect and tunable valley splitting in 2D CrGeTe3/MTe2 (M = Mo, W) van der Waals heterostructures

Proximity-induced magnetic exchange interactions offer a novel approach to manipulate the valley degree of freedom (DOF) in nonmagnetic monolayers without external magnetic fields. Transition metal dichalcogenides (TMDs) serve as an ideal platform for valleytronics research. Here, by introducing a two-dimensional (2D) magnetic substrate, chromium germanium telluride (CrGeTe₃), we demonstrate effective control over the spin and valley properties of CrGeTe₃/MTe₂ (M = Mo, W) van der Waals (vdW) heterostructures. Our first-principles calculations and $k\bullet p$ model Hamiltonian analysis reveal that the magnetic proximity effect (MPE) induces valley splitting and polarization in monolayer MoTe₂ and WTe₂ through the synergistic action of spin-orbit coupling (SOC) and proximity exchange interactions. Further investigation shows that valley splitting in these heterostructures is highly sensitive to the overlap between the atomic projection positions of TMDs and the magnetic Cr atoms, and can be continuously adjusted by varying the magnetization of CrGeTe₃. Additionally, normal strain and experimentally accessible electric fields can effectively modulate the proximity exchange coupling, thus enabling extensive tunability of valley splitting. These controllable manipulations of the valley DOF through external stimuli mark a significant advancement in valleytronics, paving the way for next-generation electronic devices with enhanced performance and novel functionalities.