Spin/valley coupled dynamics of electrons and holes at the ${\text{MoS}}_2-{\text{MoSe}}_2$ interface

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.

15 + 6 pages; 4 + 3 figures

References in corpus (10)

• Valley polarization in MoS2 monolayers by optical pumping
• Ultrafast Charge Transfer in Atomically Thin MoS2/WS2 Heterostructures
• The Valley Hall Effect in MoS2 Transistors
• Observation of Long-Lived Interlayer Excitons in Monolayer MoSe2-WSe2 Heterostructures
• Tightly bound excitons in monolayer WSe2
• Ultrafast Manipulation of Valley Pseudospin
• Directional Interlayer Spin-Valley Transfer in Two-Dimensional Heterostructures
• Valley relaxation of resident electrons and holes in a monolayer semiconductor: Dependence on carrier density and the role of substrate-induced disorder
• Observation of Ultralong Valley Lifetime in WSe2/MoS2 Heterostructures
• Time-resolved Kerr rotation spectroscopy of valley dynamics in single-layer MoS2

Cited by in corpus (4)

• Twist angle dependent interlayer transfer of valley polarization from excitons to free charge carriers in WSe${}_2$/MoSe${}_2$ heterobilayers
• Realization of valley-spin polarized current via parametric pump in monolayer $\mathrm{Mo}{\mathrm{S}}_2$
• Probing the formation of dark interlayer excitons via ultrafast photocurrent
• Light-matter interactions in layered materials and heterostructures: from moiré physics and magneto-optical effects to ultrafast dynamics and hybrid meta-photonics