Magnetic Proximity Induced Giant Enhancement of Valley Polarization and Zeeman Splitting in WS2/Fe3GaTe2 Heterostructures

Substrate engineering offers a powerful approach to tailoring quasiparticle interactions in two-dimensional (2D) materials for valley-quantum devices. Here, a significantly enhanced valley polarization of 67% has been observed in a WS2 monolayer on a thin Fe3GaTe2 (FGT) layer under far-off resonant excitation at 10 K, which is much higher than that of 16% detected from WS2 monolayer. This enhancement is attributed to the magnetic proximity effect, which leads to a shorter exciton lifetime in the heterostructure without affecting the valley scattering time. The temperature dependence of valley polarization strongly correlates with the thermomagnetic behavior of the FGT film, suggesting a strong exciton–magnon coupling. Additionally, we observe a valley Zeeman splitting of −5 meV, corresponding to an effective Landé g-factor of −66.03, supported by first-principles calculations. These findings underscore the importance of substrate engineering in modulating intrinsic valley carriers of ultrathin 2D materials, opening new avenues for valleytronic devices.