Control of the valley polarization of monolayer WSe<sub>2</sub> by Dexter-like coupling

Jakub Jasiński; Joshua J P Thompson; Swaroop Palai; Maciej Śmiertka; Mateusz Dyksik; Takashi Taniguchi; Kenji Watanabe; Michał Baranowski; Duncan K Maude; Alessandro Surrente; Ermin Malic; Paulina Płochocka

doi:10.1088/2053-1583/ad1ae8

論文 Control of the valley polarization of monolayer WSe₂ by Dexter-like coupling

Jakub Jasiński ; Joshua J P Thompson ; Swaroop Palai ; Maciej Śmiertka ; Mateusz Dyksik ; Takashi Taniguchi (National Institute for Materials Science) ; Kenji Watanabe (National Institute for Materials Science) ; Michał Baranowski ; Duncan K Maude ; Alessandro Surrente ; Ermin Malic ; Paulina Płochocka

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Jakub Jasiński, Joshua J P Thompson, Swaroop Palai, Maciej Śmiertka, Mateusz Dyksik, Takashi Taniguchi, Kenji Watanabe, Michał Baranowski, Duncan K Maude, Alessandro Surrente, Ermin Malic, Paulina Płochocka. Control of the valley polarization of monolayer WSe₂ by Dexter-like coupling. 2D Materials. 2024, 11 (2), 025007. https://doi.org/10.1088/2053-1583/ad1ae8

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(abstract)

Intervalley scattering mechanisms govern the dynamics of excitonic complexes in transition metal dichalcogenide monolayers. Here, we investigate the excitation energy dependence of the valley polarization of excitons in a WSe2 monolayer. We observe that the valley polarization drastically decreases when the excitation is resonant with the B1s resonance. This behaviour can be explained by a Dexter-like coupling in the momentum space between exciton states residing in opposite valleys but with the same spin configuration. This induces a net transfer of the exciton population from the optically driven valley towards the opposite, undriven valley. We observe the long-term fingerprints of this population transfer, as a vanishing valley polarization for the neutral exciton, and a negative valley polarization for biexcitonic complexes, in qualitative agreement with theoretical predictions based on a fully microscopic many-particle approach. This, together with a decrease of the PL energy when the excitation is resonant with the B1s state, points to the prominent role of the Dexter-like coupling in the exciton dynamics of atomically thin semiconductors.

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