Nonclassical Exciton Diffusion in Monolayer WSe2

Abstract

We experimentally demonstrate time-resolved exciton propagation in a monolayer semiconductor at cryogenic temperatures. Monitoring phonon-assisted recombination of dark states, we find a highly unusual case of exciton diffusion. While at 5 K the diffusivity is intrinsically limited by acoustic phonon scattering, we observe a pronounced decrease of the diffusion coefficient with increasing temperature, far below the activation threshold of higher-energy phonon modes. This behavior corresponds neither to well-known regimes of semiclassical free-particle transport nor to the thermally activated hopping in systems with strong localization. Its origin is discussed in the framework of both microscopic numerical and semi-phenomenological analytical models illustrating the observed characteristics of nonclassical propagation. Challenging the established description of mobile excitons in monolayer semiconductors, these results open up avenues to study quantum transport phenomena for excitonic quasiparticles in atomically-thin van der Waals materials and their heterostructures.

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Cited by in corpus (26)

• Exciton optics, dynamics and transport in atomically thin semiconductors
• Dark exciton-exciton annihilation in monolayer WSe${}_2$
• Interaction-driven transport of dark excitons in 2D semiconductors with phonon-mediated optical readout
• Extended spatial coherence of interlayer excitons in MoSe${}_2$/WSe${}_2$ heterobilayers
• Exciton-exciton interactions in van der Waals heterobilayers
• Visualization of dark excitons in semiconductor monolayers for high-sensitivity strain sensing
• Hole- and electron-injection driven phase transitions in transition metal dichalcogenides and beyond: A unified understanding
• Microscopic modelling of exciton-polariton diffusion coefficients in atomically thin semiconductors
• Theory of coherent phonons coupled to excitons
• Ultrafast pseudospin quantum beats in multilayer WSe${}_2$ and MoSe${}_2$
• Impact of atomic reconstruction on optical spectra of twisted TMD homobilayers
• Phonon-induced exciton weak localization in two-dimensional semiconductors
• 2D material exciton-polariton transport on 2D photonic crystals
• Coherent spin dynamics of excitons in strained monolayer semiconductors
• Electron dynamics in a 2D nanobubble: A two-level system based on spatial density
• Viscous hydrodynamics of excitons in van der Waals heterostructures
• Two dimensional semiconductors: optical and electronic properties
• Stability of Wigner crystals and Mott insulators in twisted moiré structures
• Signatures of valley drift in the diversified band dispersions of bright, gray, and dark excitons in MoS2 monolayers under uni-axial strains
• Impact of an electron Wigner crystal on exciton propagation
• Polariton transport in 2D semiconductors: Phonon-mediated transitions between ballistic, superdiffusive and exciton-limited regimes
• Spectral asymmetry of phonon sideband luminescence in monolayer and bilayer WSe2
• Boltzmann transport theory of magnon-exciton drag
• Strain-induced exciton mobility in layered WS2 from first principles
• Phonon-induced Markovian and non-Markovian effects on absorption spectra of moiré excitons in twisted transition metal dichalcogenide bilayers
• Trion-phonon interaction in atomically thin semiconductors