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

Mark Danovich, Viktor Zolyomi, Vladimir Fal'ko

    Research output: Contribution to journalArticlepeer-review


    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 ⇆ 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 ~10 ps, and analyse how these complexes appear in the temperature-dependent photoluminescence spectra of WS2 and WSe2 monolayers.
    Original languageEnglish
    Article number45998
    JournalScientific Reports
    Early online date6 Apr 2017
    Publication statusPublished - 2017

    Research Beacons, Institutes and Platforms

    • National Graphene Institute


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