Relaxation and darkening of excitonic complexes in electrostatically-doped monolayer semiconductors: Roles of exciton-electron and trion-electron interactions

Abstract

We present photoluminescence measurements in monolayer WSe${}_2$, which point to the importance of the interaction between charged particles and excitonic complexes. The theoretical analysis highlights the key role played by exchange scattering, referring to cases wherein the particle composition of the complex changes after the interaction. For example, exchange scattering renders bright excitonic complexes dark in monolayer WSe${}_2$ on accounts of the unique valley-spin configuration in this material. In addition to the ultrafast energy relaxation of hot excitonic complexes following their interaction with electrons or holes, our analysis sheds light on several key features that are commonly seen in the photoluminescence of this monolayer semiconductor. In particular, we can understand why the photoluminescence intensity of the neutral bright exciton is strongest when the monolayer is hole-doped rather than charge neutral or electron-doped. Or the reason for the dramatic increase of the photoluminescence intensity of negatively-charged excitons (trions) as soon as electrons are added to the monolayer. To self-consistently explain the findings, we further study the photoluminescence spectra at different excitation energies and analyze the behavior of the elusive indirect exciton.

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• Interaction-driven transport of dark excitons in 2D semiconductors with phonon-mediated optical readout
• Strain control of exciton and trion spin-valley dynamics in monolayer transition metal dichalcogenides
• Trion photoluminescence and trion stability in atomically thin semiconductors
• Composite excitonic states in doped semiconductors
• Emergence of 6-particle "hexciton'' states in WS${}_2$ and MoSe${}_2$ monolayers
• Excitons and trions in monolayer semiconductors with correlated electrons
• The effect of dielectric environment on the brightening of neutral and charged dark excitons in WSe${}_2$ monolayer
• Excitons and trions in WSSe monolayers
• Intervalley electron-hole exchange interaction and impurity-assisted recombination of indirect excitons in WS${}_2$ and WSe${}_2$ monolayers
• Charge-carrier complexes in monolayer semiconductors
• Trion formation resolves observed peak shifts in the optical spectra of transition metal dichalcogenides
• Dark exciton energy splitting in monolayer WSe2: insights from time-dependent density-functional theory
• Excitons in periodic potentials
• Component exchange theory of trions
• Energy shifts and broadening of excitonic resonances in electrostatically-doped semiconductors
• Electron density control in tungsten diselenide monolayers via photochlorination
• Trion-phonon interaction in atomically thin semiconductors