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Measurement of the conduction band spin-orbit splitting in $\mathrm{WSe_2}$ and $\mathrm{WS_2}$ monolayers

We have investigated charge tunable devices based on $\mathrm{WSe_2}$ and $\mathrm{WS_2}$monolayers encapsulated in hexagonal boron nitride. In addition to the well-known radiative recombination of neutral and charged excitons, stationary photoluminescence measurements highlight a weaker-intensity o...

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Bibliographic Details
Published in:Physical review. B 2023-06, Vol.107 (24)
Main Authors: Ren, Lei, Robert, Cedric, Dery, Hanan, He, Minhao, Li, Pengke, Van Tuan, Dinh, Renucci, Pierre, Lagarde, Delphine, Taniguchi, Takashi, Watanabe, Kenji, Xu, Xiaodong, Marie, Xavier
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Language:English
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Summary:We have investigated charge tunable devices based on $\mathrm{WSe_2}$ and $\mathrm{WS_2}$monolayers encapsulated in hexagonal boron nitride. In addition to the well-known radiative recombination of neutral and charged excitons, stationary photoluminescence measurements highlight a weaker-intensity optical transition that appears when the monolayer is electrostatically doped with electrons. We have carried out a detailed characterization of this photoluminescence line based on its doping dependence, its variation as a function of the optical excitation power, its polarization characteristics, and its g factor measured under longitudinal magnetic field. We interpret this luminescence peak as an impurity-assisted radiative recombination of the intervalley negatively charged exciton (triplet trion). In addition to the standard direct recombination, the triplet trion has a second recombination channel triggered by elastic scattering off the short-range impurity potential. The energy difference between the emitted photons from these two possible recombination processes of the same triplet trion is simply the single-particle conduction band spin-orbit splitting Δc. We measure Δc= 12 ± 0.5 meV for the $\mathrm{WSe_2}$ monolayer and Δc= 12 ± 1 meV for the $\mathrm{WS_2}$ monolayer. Here, these results demonstrate the importance of second-order exciton recombination processes in transition-metal dichalcogenide structures.
ISSN:2469-9950
2469-9969