Dark trions and biexcitons in WS2 and WSe2 made bright by e-e scattering

Abstract

The direct band gap character and large spin-orbit splitting of the valence band edges (at the K and K' valleys) in monolayer transition metal dichalcogenides have put these two-dimensional materials under the spot-light of intense experimental and theoretical studies. In particular, for Tungsten dichalcogenides it has been found that the sign of spin splitting of conduction band edges makes ground state excitons radiatively inactive (dark) due to spin and momentum mismatch between the constituent electron and hole. One might similarly assume that the ground states of charged excitons and biexcitons in these monolayers are also dark. Here, we show that the intervalley K$\leftrightarrows$K' electron-electron scattering mixes bright and dark states of these complexes, and estimate the radiative lifetimes in the ground states of these "semi-dark" trions and biexcitons to be ~ 10ps, and analyse how these complexes appear in the temperature-dependent photoluminescence spectra of WS2 and WSe2 monolayers.

29 pages including supplementary material

References in corpus (7)

• Valley polarization in MoS2 monolayers by optical pumping
• k.p theory for two-dimensional transition metal dichalcogenide semiconductors
• Magnetic brightening and control of dark excitons in monolayer WSe2
• Measurement of high exciton binding energy in the monolayer transition-metal dichalcogenides WS2 and WSe2
• Brightening of dark excitons in monolayers of semiconducting transition metal dichalcogenides
• Binding energies of trions and biexcitons in two-dimensional semiconductors from diffusion quantum Monte Carlo calculations
• Auger recombination of dark excitons in $\mathrm{W}{\mathrm{S}}_2$ and $\mathrm{WS}{\mathrm{e}}_2$ monolayers

Cited by in corpus (24)

• Charged excitons in monolayer WSe${}_2$: experiment and theory
• Dark excitons in transition metal dichalcogenides
• Biexciton fine structure in monolayer transition metal dichalcogenides
• Gate tunable dark trions in monolayer WSe${}_2$
• Optical properties of charged excitons in two-dimensional semiconductors
• Diffusion quantum Monte Carlo study of excitonic complexes in two-dimensional transition-metal dichalcogenides
• Zeeman Splitting and Inverted Polarization of Biexciton Emission in Monolayer WS2
• Marrying excitons and plasmons in monolayer transition-metal dichalcogenides
• Mapping of the dark exciton landscape in transition metal dichalcogenides
• Hexcitons and oxcitons in monolayer WSe${}_2$
• Excitonic complexes in $n$-doped WS${}_2$ monolayer
• Quartet states in two-electron quantum dots in bilayer graphene
• Relaxation and darkening of excitonic complexes in electrostatically-doped monolayer semiconductors: Roles of exciton-electron and trion-electron interactions
• Strong Valley Zeeman Effect of Dark Excitons in Monolayer Transition Metal Dichalcogenides in a Tilted Magnetic Field
• Interaction-driven transport of dark excitons in 2D semiconductors with phonon-mediated optical readout
• Charged exctions in two-dimensional transition-metal dichalcogenides - semiclassical calculation of Berry-curvature effects
• Leaky exciton condensates in transition metal dichalcogenide moiré bilayers
• Interplay of Excitonic Complexes in $p$-Doped WSe${}_2$ Monolayers
• Incoherent phonon population and exciton-exciton annihilation in monolayer WS2 revealed by time-resolved spontaneous Raman scattering
• Light-matter coupling and non-equilibrium dynamics of exchange-split trions in monolayer WS2
• Charge-carrier complexes in monolayer semiconductors
• Valley-mediated singlet- and triplet-polaron interactions and quantum dynamics in a doped WSe${}_2$ monolayer
• Electrostatic control of the trion fine structure in transition metal dichalcogenide monolayers
• Increased formation of trions and charged biexcitons by above-gap excitation in single-layer $WS{e}_2$