Layer- and Charge-State Dependent Magnetic Proximity Modulation of Valley Excitons in MoS₂/CrBr₃ Heterostructures

The manipulation of valley degrees of freedom in transition metal dichalcogenides (TMDCs) via the magnetic proximity effect (MPE) is key to advancing next-generation quantum and optoelectronic technologies. However, a comprehensive understanding of how MPE depends on layer configuration and excitonic charge state remains elusive. Here, a systematic study is reported on MPE-induced magneto-optical responses in monolayer and bilayer MoS₂ interfaced with few and bulk CrBr₃. Photoluminescence spectroscopy reveals a charge state dependent MPE, consistent with a spin-aligned interfacial charge transfer mechanism. Notably, CrBr₃ introduces significant Zeeman splitting in 1L-MoS₂, with a large splitting of 1.49 meV at zero field, consistent with the theoretical calculation of 1.8 meV. Under high magnetic fields, the g-factors of neutral excitons and trions are enhanced by factors of ≈2.3 and ≈1.8, respectively. In contrast, bilayer MoS₂ exhibits a weaker response, highlighting the diminished interfacial exchange coupling in multilayer systems. The findings demonstrate a robust MPE in CrBr₃-based heterostructures and provide critical insights into layer and charge state-dependent proximity effects, paving the way for tailored valleytronic functionalities in 2D materials.