Excitons bound by photon exchange

Year: 2021

Authors: Cortese E., Tran NL., Manceau JM., Bousseksou A., Carusotto I., Biasiol G., Colombelli R., De Liberato S.

Autors Affiliation: University of Southampton; Universite Paris Cite; Institut Polytechnique de Paris; Ecole Polytechnique; Centre National de la Recherche Scientifique (CNRS); CNRS – Institute of Physics (INP); Universite Paris Saclay; Consiglio Nazionale delle Ricerche (CNR); Istituto Nazionale di Ottica (INO-CNR); University of Trento; University of Trento; Consiglio Nazionale delle Ricerche (CNR); Istituto Officina dei Materiali (IOM-CNR)

Abstract: Electrons and holes in doped quantum wells cannot form bound states from usual Coulomb interaction. However, when the system is embedded in a cavity, the exchange of photons provides an effective attraction, leading to the creation of bound excitons. In contrast to interband excitons in undoped quantum wells, doped quantum wells do not display sharp resonances due to excitonic bound states. The effective Coulomb interaction between electrons and holes in these systems typically leads to only a depolarization shift of the single-electron intersubband transitions(1). Non-perturbative light-matter interaction in solid-state devices has been investigated as a pathway to tuning optoelectronic properties of materials(2,3). A recent theoretical work(4)predicted that when the doped quantum wells are embedded in a photonic cavity, emission-reabsorption processes of cavity photons can generate an effective attractive interaction that binds electrons and holes together, leading to the creation of an intraband bound exciton. Here, we spectroscopically observe such a bound state as a discrete resonance that appears below the ionization threshold only when the coupling between light and matter is increased above a critical value. Our result demonstrates that two charged particles can be bound by the exchange of transverse photons. Light-matter coupling can thus be used as a tool in quantum material engineering, tuning electronic properties of semiconductor heterostructures beyond those permitted by mere crystal structures, with direct applications to mid-infrared optoelectronics.

Journal/Review: NATURE PHYSICS

Volume: 17 (1)      Pages from: 31  to: 35

More Information: S.D.L. is a Royal Society Research Fellow and was partly funded by the Philip Leverhulme Prize of the Leverhulme Trust. R.C., J.M.-M., G.B. and I.C. were partly funded by the European Union FET-Open Grant Number MIR -BOSE 737017. R.C. and A.B. were partly funded by the French National Research Agency (project IRENA). This work was partly supported by the French RENATECH network.
KeyWords: Light-matter coupling, doped quantum wells, quantum material engineering
DOI: 10.1038/s41567-020-0994-6

Citations: 28
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