Tailoring Exciton Anisotropy and Valley via Magnetic Layer Thickness in 2D Heterostructures.

The magnetic proximity effect offers a promising route to tailor the excitonic properties of transition metal dichalcogenides (TMDCs) via adjacent magnetic materials. While previous studies mainly focus on single-thickness magnetic materials, the layer-dependent exciton regulation remains largely underexplored. Here, ferromagnetic CrGeTe (CGT) is used as a platform to explore the exciton performance regulation of TMDCs. Employing low-temperature, high-magnetic-field photoluminescence spectroscopy reveals a pronounced thickness-dependent modulation of exciton behavior. Circularly polarized PL measurements reveal distinct magnetic responses at the MoSe and WSe interfaces, attributed to strong super-super exchange coupling at the WSe-CGT interface. Valley polarization of WSe excitons is dependent on CGT thickness, and the valley polarization is enhanced by 3 times by a thin layer of CCT. Further study shows that the linear polarization response of WSe decays rapidly with the increase of CGT, indicating that CGT modulates linear polarization by regulating the exciton valley coherence time. These findings establish magnetic layer thickness as a crucial parameter for controlling exciton dynamics in TMDCs, offering new design strategies for magneto-optical and valleytronic devices based on van der Waals heterostructures.