Unveiling Ultrafast Spin‐Valley Dynamics and Phonon‐Mediated Charge Transfer in MoSe ₂ /WSe ₂ Heterostructures

Abstract Helicity‐resolved ultrafast transient absorption spectroscopy is used to study spin‐valley polarization dynamics in a vertically stacked MoSe ₂ /WSe ₂ heterostructure. The experimental findings reveal details of interlayer charge transfer on ultrafast timescales, showing that the spin‐valley polarized state of photoexcited carriers is conserved during the charge transfer and formation of interlayer excitons. These results confirm that phonon scattering mediates the interlayer charge transfer process, while a high phonon population at elevated temperatures causes a significant decrease in spin‐valley selective charge transfer. Moreover, the experimental findings demonstrate the possibility that interlayer excitons and their spin‐valley polarization can be probed in the optical response of intralayer excitons. These findings pave the way for ultrafast detection, control, and manipulation of spin‐valley polarized excitons in transition metal dichalcogenide‐based 2D heterostructures.