Strong quantum interaction between excitons bound by cavity photon exchange

TL;DR

This paper predicts and analyzes how cavity photon exchange can induce strong, tunable interactions between excitons in doped quantum wells, potentially enabling giant nonlinearities in infrared quantum optics.

Contribution

It introduces a theoretical framework for exciton-photon bound states with tunable binding energy and enhanced interactions, revealing a Rydberg-like regime in solid-state systems.

Findings

Exciton binding energy can be tuned via cavity frequency.

Polariton-polariton interactions are significantly enhanced in this regime.

Potential for giant quantum optical nonlinearities in infrared spectrum.

Abstract

We theoretically predict the interaction between polaritonic excitations arising from the coupling of a cavity photon mode with bound to continuum intersubband transitions in a doped quantum well. The resulting exciton bound by photon exchange, recently demonstrated experimentally, exhibits a binding energy that can be continuously tuned by varying the cavity frequency. We show that polariton-polariton interactions, originating from both Coulomb interactions and Pauli blocking, can be dramatically enhanced by reducing the exciton binding energy, thereby increasing the effective Bohr radius along the growth direction. This regime is reminiscent of Rydberg atoms, where weak binding leads to strong quantum interactions. Our predictions indicate that this physics can give rise to giant quantum optical nonlinearities in the mid and far infrared, a spectral region that remains largely unexplored in quantum optics and offers exciting opportunities for both fundamental studies and applications.