Unveiling Ultrafast Spin-Valley Dynamics and Phonon-Mediated Charge Transfer in MoSe$_{2}$/WSe$_{2}$ Heterostructures

TL;DR

This study uses ultrafast spectroscopy to reveal how spin-valley polarization is conserved during charge transfer in MoSe₂/WSe₂ heterostructures, highlighting phonon scattering's role and implications for ultrafast optoelectronic control.

Contribution

It provides new insights into ultrafast spin-valley dynamics and phonon-mediated charge transfer in 2D heterostructures, advancing understanding of exciton behavior.

Findings

Spin-valley polarization is conserved during interlayer charge transfer.

Phonon scattering mediates the charge transfer process.

High temperature reduces spin-valley selective transfer.

Abstract

We use helicity-resolved ultrafast transient absorption spectroscopy 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. Our 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.