Ultrafast dynamics in monolayer TMDCs: the interplay of dark excitons, phonons and intervalley Coulomb exchange

Abstract

Understanding the ultrafast coupling and relaxation mechanisms between valleys in transition metal dichalcogenide semiconductors is of crucial interest for future valleytronic devices. Recent ultrafast pump-probe experiments showed an unintuitive significant bleaching at the excitonic $B$ transition after optical excitation of the energetically lower excitonic $A$ transition. Here, we present a possible microscopic explanation for this surprising effect. It is based on the joint action of exchange coupling and phonon-mediated thermalization into dark exciton states and does not involve a population of the B exciton. Our work demonstrates how intra- and intervalley coupling on a femtosecond timescale governs the optical valley response of 2D semiconductors.

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Cited by in corpus (33)

• The ultrafast onset of exciton formation in 2D semiconductors
• Multipath optical recombination of intervalley dark excitons and trions in monolayer WSe${}_2$
• Exciton-Scattering-Induced Dephasing in Two-Dimensional Semiconductors
• Theory of exciton dynamics in time-resolved ARPES: intra- and intervalley scattering in two-dimensional semiconductors
• Exciton optics, dynamics and transport in atomically thin semiconductors
• Nonequilibrium Lattice Dynamics in Monolayer MoS2
• MoSi${}_2$N${}_4$-like crystals -- the new family of two-dimensional materials
• Time-domain observation of interlayer exciton formation and thermalization in a MoSe${}_2$/WSe${}_2$ heterostructure
• Momentum-Resolved Exciton Coupling and Valley Polarization Dynamics in Monolayer WS${}_2$
• Optical dipole orientation of interlayer excitons in MoSe${}_2$-WSe${}_2$ heterostacks
• Phonon-assisted inter-valley scattering determines ultrafast exciton dynamics in MoSe${}_2$ bilayers
• Quenching of Intervalley Exchange Coupling in the Presence of Momentum-Dark States in TMDCs
• Spatially indirect intervalley excitons in bilayer WSe2
• Exciton-phonon-scattering: A competition between bosonic and fermionic nature of bound electron-hole pairs
• Interlayer exciton valley polarization dynamics in large magnetic fields
• 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
• Ultrafast photocurrent and absorption microscopy of few-layer TMD devices isolate rate-limiting dynamics driving fast and efficient photoresponse
• Phonon signatures in spectra of exciton polaritons in transition metal dichalcogenides
• Excitonic theory of doping-dependent optical response in atomically thin semiconductors
• Distance dependence of the energy transfer mechanism in WS${}_2$-graphene heterostructures
• 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
• Effect of intravalley and intervalley electron-hole exchange on the nonlinear optical response of monolayer MoSe${}_2$
• Ultrafast Phonon-Diffuse Scattering as a Tool for Observing Chiral Phonons in Monolayer Hexagonal Lattices
• Probing spin dynamics of 2D excitons with twisted light
• Dynamic screening of quasiparticles in WS${}_2$ monolayers
• Electrostatic control of the trion fine structure in transition metal dichalcogenide monolayers
• Fermionic vs. bosonic thermalization in the phonon-driven exciton dynamics: An analytic dimensionality study
• Dissecting intervalley coupling mechanisms in monolayer transition metal dichalcogenides
• Data-Driven Forecasting of Non-Equilibrium Solid-State Dynamics
• Valley polarization fluctuations, bistability, and switching in two-dimensional semiconductors
• Suppression and amplification of phonon sidebands in transition metal dichalcogenides by optical feedback