Quenching of Intervalley Exchange Coupling in the Presence of Momentum-Dark States in TMDCs

Abstract

Monolayers of transition metal dichalcogenides are promising materials for valleytronic applications, since they possess two individually addressable excitonic transitions at the non-equivalent $K$ and $K^{\prime }$ points with different spins, selectively excitable with light of opposite circular polarization. Here, it is of crucial importance to understand the elementary processes determining the lifetime of these optically injected valley excitons. In this study, we perform microscopic calculations based on a Heisenberg equation of motion formalism to investigate the efficiency of the intervalley coupling in the presence (W based TMDCs) and absence (Mo based TMDCs) of energetically low lying momentum-dark exciton states. While we predict a valley exciton lifetime on the order of some hundreds of fs in the absence of low lying momentum-dark states we demonstrate a strong quenching of the valley lifetime in the presence of such states.

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Cited by in corpus (20)

• The ultrafast onset of exciton formation in 2D semiconductors
• Exciton-Scattering-Induced Dephasing in Two-Dimensional Semiconductors
• Momentum-Resolved Exciton Coupling and Valley Polarization Dynamics in Monolayer WS${}_2$
• Phonon-assisted inter-valley scattering determines ultrafast exciton dynamics in MoSe${}_2$ bilayers
• Brightening of spin- and momentum-dark excitons in transition metal dichalcogenides
• Enhancement of Exciton Valley Polarization in Monolayer MoS2 Induced by Scattering
• Exciton-phonon-scattering: A competition between bosonic and fermionic nature of bound electron-hole pairs
• Control of the exciton valley dynamics in van der Waals heterostructures
• Impact of dark excitons on Förster type resonant energy transfer between dye molecules and atomically thin semiconductors
• Theory of the Coherent Response of Magneto-Excitons and Magneto-Biexcitons in Monolayer Transition Metal Dichalcogenides
• Impact of optically pumped non-equilibrium steady states on luminescence emission of atomically-thin semiconductor excitons
• Valley-exchange coupling probed by angle-resolved photoluminescence
• Theory of radial oscillations in metal nanoparticles driven by optically induced electron density gradients
• Phonon-mediated exciton capture in Mo-based transition metal dichalcogenides
• Fermionic vs. bosonic thermalization in the phonon-driven exciton dynamics: An analytic dimensionality study
• Transition from Optically Excited to Intrinsic Spin Polarization in WSe${}_2$
• Dissecting intervalley coupling mechanisms in monolayer transition metal dichalcogenides
• Valley polarization fluctuations, bistability, and switching in two-dimensional semiconductors
• Valley-controlled many-body exciton interactions in monolayer WSe${}_2$ phototransistors
• Suppression and amplification of phonon sidebands in transition metal dichalcogenides by optical feedback