Tunable Proximity Valley Splitting Via Interfacial Exchange Pinning in WSe2-CrBr3-CrPS4 Heterostructures.

Magnetic proximity effects in van der Waals heterostructures provide an optical route to manipulate valley pseudospins in transition-metal dichalcogenides, but abrupt switching of two-dimensional (2D) ferromagnets (FM) limits continuous valley modulation. We demonstrate that the proximity-induced valley response of WSe2 can be modified by engineering the interfacial magnetic environment in WSe2-CrBr3-CrPS4 heterostructures. Circularly polarized magneto-photoluminescence reveals robust nonvolatile valley polarization in WSe2-CrBr3 with a pronounced low-field hysteresis tracking CrBr3 magnetization. Spectroscopy and calculations indicate that spin-selective interfacial charge transfer and orbital hybridization enhance the proximity exchange field and valley Zeeman splitting. Introducing antiferromagnetic (AFM) CrPS4 weakens the degree of circular polarization modulation and broadens the low-field valley polarization reversal, consistent with an interfacial AFM/FM exchange pinning scenario. These results show that interfacial magnetic engineering can tailor proximity-induced valley responses in 2D heterostructures.