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Comptes Rendus. Physique
Exciton–polarons in two-dimensional semiconductors and the Tavis–Cummings model
[Exciton–polarons dans des semi-conducteurs bidimensionnels et le modèle de Tavis–Cummings]
Comptes Rendus. Physique, Online first (2021), pp. 1-8.

Article du numéro thématique : Recent advances in 2D material physics
[Physique du solide 2D]

Les excitations optiques élémentaires d’un système bidimensionnel d’électrons ou de trous ont été identifiées comme des exciton-Fermi-polarons. Néanmoins, la connexion entre l’état lié d’un exciton et d’un électron, appelé trion, et les exciton–polarons fait l’objet d’un débat permanent. Ici, nous utilisons une analogie avec le modèle de Tavis–Cummings de l’optique quantique pour montrer qu’un exciton–polaron peut être compris comme une quasi-particule hybride — une superposition cohérente d’un exciton nu dans une mer de Fermi non perturbée et une excitation collective brillante de nombreux trions. L’analogie est valable dans la mesure où l’Ansatz de Chevy fournit une bonne description de l’écrantage dynamique des excitons et à condition que l’énergie de Fermi soit beaucoup plus petite que l’énergie de liaison des trions. Nous espérons que nos résultats apporteront de nouvelles connaissances qui pourraient aider à expliquer les différences frappantes entre les spectres d’absorption et d’émission des semi-conducteurs bidimensionnels.

The elementary optical excitations of a two-dimensional electron or hole system have been identified as exciton-Fermi-polarons. Nevertheless, the connection between the bound state of an exciton and an electron, termed trion, and exciton–polarons is subject of ongoing debate. Here, we use an analogy to the Tavis–Cummings model of quantum optics to show that an exciton–polaron can be understood as a hybrid quasiparticle—a coherent superposition of a bare exciton in an unperturbed Fermi sea and a bright collective excitation of many trions. The analogy is valid to the extent that the Chevy Ansatz provides a good description of dynamical screening of excitons and provided the Fermi energy is much smaller than the trion binding energy. We anticipate our results to bring new insight that could help to explain the striking differences between absorption and emission spectra of two-dimensional semiconductors.

Première publication :
DOI : https://doi.org/10.5802/crphys.47
Mots clés : Exciton–polarons, Semi-conducteurs bidimensionnels, Modèle de Tavis–Cummings, Optique quantique, Physique des corps multiples
@article{CRPHYS_2021__22_S4_A4_0,
     author = {Atac Imamoglu and Ovidiu Cotlet and Richard Schmidt},
     title = {Exciton{\textendash}polarons in two-dimensional semiconductors and the {Tavis{\textendash}Cummings} model},
     journal = {Comptes Rendus. Physique},
     publisher = {Acad\'emie des sciences, Paris},
     year = {2021},
     doi = {10.5802/crphys.47},
     language = {en},
     note = {Online first},
}
Atac Imamoglu; Ovidiu Cotlet; Richard Schmidt. Exciton–polarons in two-dimensional semiconductors and the Tavis–Cummings model. Comptes Rendus. Physique, Online first (2021), pp. 1-8. doi : 10.5802/crphys.47.

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