Twist angle dependent interlayer transfer of valley polarization from excitons to free charge carriers in WSe${}_2$/MoSe${}_2$ heterobilayers

Abstract

We identify an optical excitation mechanism that transfers a valley polarization from photo-excited electron-hole pairs to free charge carriers in twisted WSe${}_2$/MoSe${}_2$ heterobilayers. For small twist angles, the valley lifetimes of the charge carriers are surprisingly short, despite the occurrence of interlayer excitons with their presumably long recombination and polarization lifetimes. For large twist angles, we measure an increase in both the valley polarization and its respective lifetime by more than two orders of magnitude. Interestingly, in such heterobilayers we observe an interlayer transfer of valley polarization from the WSe${}_2$ layer into the MoSe${}_2$ layer. This mechanism enables the creation of a photo-induced valley polarization of free charge carriers in MoSe${}_2$, which amplitude scales with the gate-induced charge carrier density. This is in contrast to monolayer MoSe${}_2$, where such a gate-tunable valley polarization cannot be achieved. By combining time-resolved Kerr rotation, photoluminesence and angle-resolved photoemission spectroscopy measurements with first principles calculations, we show that these findings can be explained by twist angle dependent interlayer scattering mechanisms involving the Q- and $\Gamma$-valleys.

21 pages, 10 figures

References in corpus (18)

• Ultrafast Charge Transfer in Atomically Thin MoS2/WS2 Heterostructures
• Observation of Long-Lived Interlayer Excitons in Monolayer MoSe2-WSe2 Heterostructures
• Exciton Valley Dynamics probed by Kerr Rotation in WSe2 Monolayers
• Twist Angle Dependent Interlayer Exciton Lifetimes in van der Waals Heterostructures
• Phonon Sidebands in Transition Metal Dichalcogenides
• Probing the spin-polarized electronic band structure in monolayer transition metal dichalcogenides by optical spectroscopy
• Ab initio calculations of ultra-short carrier dynamics in 2D materials: valley depolarization in single-layer WSe${}_2$
• Exciton Trapping Is Responsible for the Long Apparent Lifetime in Acid-Treated MoS2
• Ultrafast charge-transfer dynamics in twisted MoS${}_2$/WSe${}_2$ heterostructures
• Hexcitons and oxcitons in monolayer WSe${}_2$
• Intrinsic Donor-Bound Excitons in Ultraclean Monolayer Semiconductors
• Exciton landscape in van der Waals heterostructures
• Valley relaxation of resident electrons and holes in a monolayer semiconductor: Dependence on carrier density and the role of substrate-induced disorder
• Spin/valley coupled dynamics of electrons and holes at the ${\text{MoS}}_2-{\text{MoSe}}_2$ interface
• Electric Field Tuning of Band Offsets in Transition Metal Dichalcogenides
• Signatures of electric field and layer separation effects on the spin-valley physics of MoSe${}_2$/WSe${}_2$ heterobilayers: from energy bands to dipolar excitons
• Ultrafast pseudospin quantum beats in multilayer WSe${}_2$ and MoSe${}_2$
• Two-color Kerr microscopy of two-dimensional materials with sub-picosecond time resolution

Cited by in corpus (7)

• Excitonic response in TMD heterostructures from first-principles: impact of stacking, twisting, and interlayer distance
• Benchmarking the integration of hexagonal boron nitride crystals and thin films into graphene-based van der Waals heterostructures
• Electrically Controlled Interfacial Charge Transfer Induced Excitons in MoSe2-WSe2 Lateral Heterostructure
• MaskTerial: A Foundation Model for Automated 2D Material Flake Detection
• Tunable resonant s-p mixing of excitons in van der Waals heterostructures
• Interacting holes in a gated WSe${}_2$ quantum channel: valley correlations and zigzag Wigner crystal
• Electrically tunable MoSe${}_2$/WSe${}_2$ heterostructure-based quantum dot