Speaker
Description
Quantum droplets are self-bound low-density configurations which may appear in ultracold gases with competing interactions. Dilute bosonic mixtures, where the attractive mean-field energy is balanced by the repulsive Lee-Huang-Yang correction stemming from quantum fluctuations, are the prototypical platform where this novel state has been first predicted [1] and shortly after experimentally observed [2,3]. Since then, quantum droplets have gained significant interest, and their study has been extended to various cold-atomic settings.
In this talk, I will show how a similar scenario can arise in a solid-state system. Specifically, we consider an atomically thin semiconductor layer embedded in an optical microcavity, where exciton-polariton quasiparticles (polaritons) result from the strong coupling between semiconductor excitons and cavity photon modes. Polaritons carry a spin degree of freedom inherited from both their matter and light components, thus resulting in the possibility
of interactions between these quasiparticles [4]. We show that the competition between the attractive spin-singlet and repulsive spin-triplet channels of the interaction can lead to the formation of a novel self-bound many-body state analogous to a quantum droplet, thus demonstrating that exciton-polaritons can display both liquid- and droplet-like phenomena.
[1] D. S. Petrov, Phys. Rev. Lett. 115, 155302 (2015)
[2] C. R. Cabrera et al., Science 359, 301 (2018)
[3] G. Semeghini et al., Phys. Rev. Lett. 120, 235301 (2018)
[4] O. Bleu, G. Li, J. Levinsen and M. M. Parish, Phys. Rev. Res. 2, 043185 (2020)
