Spin-Selective Defect Coupling Drives Valley Polarization and Dynamics in Vanadium-Doped Monolayer MoS ₂

Controlling the valley degree of freedom in two-dimensional transition metal dichalcogenides (TMDCs) is crucial for enabling valleytronic and optoelectronic applications. Herein, we investigate how substitutional-doping-induced defects influence valley properties and dynamics in monolayer MoS2. Using helicity-resolved transient absorption spectroscopy, we reveal that vanadium doping introduces local magnetic proximity effects that modify valley-polarized excitonic relaxation pathways. The vanadium-induced defect states are spin-polarized and exhibit valley-like characteristics, forming a three-valley system that sustains a finite degree of valley polarization (DVP) at room temperature. We observe significantly extended valley lifetimes in doped samples compared with pristine MoS2 and uncover a clear dependence of valley properties on vanadium concentration. Furthermore, we demonstrate that interband transitions can be harnessed to selectively manipulate excitonic relaxation, resulting in enhanced DVP. These findings establish a route for tuning valley lifetimes and intervalley scattering through targeted doping, offering new design strategies for next-generation spin-valleytronic devices.