Spin/valley coupled dynamics of electrons and holes at the ${\text{MoS}_{2}-\text{MoSe}_{2}}$ interface

TL;DR

This study investigates spin and valley dynamics of electrons and holes at the MoS2-MoSe2 interface, revealing spin conservation during tunneling and differing depolarization rates linked to spin-orbit splitting, advancing TMD-based spintronics.

Contribution

It provides new insights into spin/valley relaxation mechanisms in TMD heterostructures, highlighting their potential for spin current generation in spintronic applications.

Findings

Electrons and holes conserve spin during tunneling across the interface.

Electrons depolarize faster than holes, with rates of ~30 ns^{-1} and <1 ns^{-1}.

Depolarization differences are related to spin-orbit splitting disparities.

Abstract

The coupled spin and valley degrees of freedom in transition metal dichalcogenides (TMDs) are considered a promising platform for information processing. Here, we use a TMD heterostructure ${\text{MoS}_{2}-\text{MoSe}_{2}}$ to study optical pumping of spin/valley polarized carriers across the interface and to elucidate the mechanisms governing their subsequent relaxation. By applying time-resolved Kerr and reflectivity spectroscopies, we find that the photoexcited carriers conserve their spin for both tunneling directions across the interface. Following this, we measure dramatically different spin/valley depolarization rates for electrons and holes, $\sim 30\,{\text{ns}}^{-1}$ and $< 1\,{\text{ns}}^{-1}$, respectively and show that this difference relates to the disparity in the spin-orbit splitting in conduction and valence bands of TMDs. Our work provides insights into the spin/valley dynamics of free carriers unaffected by complex excitonic processes and establishes TMD heterostructures as generators of spin currents in spin/valleytronic devices.