Observation of exciton-exciton interaction mediated valley depolarization in monolayer MoSe${}_2$

Abstract

The valley pseudospin in monolayer transition metal dichalcogenides (TMDs) has been proposed as a new way to manipulate information in various optoelectronic devices. This relies on a large valley polarization that remains stable over long timescales (hundreds of ns). However, time resolved measurements report valley lifetimes of only a few ps. This has been attributed to mechanisms such as phonon-mediated inter-valley scattering and a precession of the valley psedospin through electron-hole exchange. Here we use transient spin grating to directly measure the valley depolarization lifetime in monolayer MoSe${}_2$. We find a fast valley decay rate that scales linearly with the excitation density at different temperatures. This establishes the presence of strong exciton-exciton Coulomb exchange interactions enhancing the valley depolarization. Our work highlights the microscopic processes inhibiting the efficient use of the exciton valley pseudospin in monolayer TMDs.

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Cited by in corpus (20)

• Nonthermal pathways to ultrafast control in quantum materials
• Exciton-Scattering-Induced Dephasing in Two-Dimensional Semiconductors
• Momentum-Resolved Exciton Coupling and Valley Polarization Dynamics in Monolayer WS${}_2$
• Exciton valley depolarization in monolayer transition-metal dichalcogenides
• Tutorial: Characterizing Microscale Energy Transport in Materials with Transient Grating Spectroscopy
• Room Temperature Terahertz Electroabsorption Modulation by Excitons in Monolayer Transition Metal Dichalcogenides
• Impact of indirect transitions on valley polarization in WS${}_2$ and WSe${}_2$
• Local field effects in ultrafast light-matter interaction measured by pump-probe spectroscopy of monolayer MoSe${}_2$
• Valley Depolarization in Monolayer Transition-Metal Dichalcogenides with Zone-Corner Acoustic Phonons
• Ultrafast Chirality-dependent Dynamics from Helicity-resolved Transient Absorption Spectroscopy
• Pump-triple sum-frequency-probe spectroscopy of transition metal dichalcogenides
• Magnetically tunable exciton valley coherence in monolayer WS${}_2$ mediated by the electron-hole exchange and exciton-phonon interactions
• Self-Induced Valley Bosonic Stimulation of Exciton-Polaritons in a Monolayer Semiconductor
• Transient Grating Spectroscopy of Photocarrier Dynamics in Semiconducting Polymer Thin Films
• Exciton-exciton Interactions -- A Quantitative Comparison Between Complimentary Phenomenological Models
• Dissecting intervalley coupling mechanisms in monolayer transition metal dichalcogenides
• A perspective on inelastic light scattering spectroscopy for probing transport of collective acoustic excitations
• Variational and field-theoretical approach to exciton-exciton interactions and biexcitons in semiconductors
• Enhancement of valley polarization at high photoexcited densities in MoS2 monolayers
• Excitonic Transport and Intervalley Scattering in Exfoliated MoSe2 Monolayer Revealed by Four-Wave-Mixing Transient Grating Spectroscopy