Supermode-Density-Wave-Polariton Condensation

TL;DR

This paper reports the observation of a novel nonequilibrium phase transition involving supermode-density-wave-polaritons in a multimode optical cavity with cold atoms, revealing complex matter-light interactions beyond mean-field theories.

Contribution

It introduces the experimental realization and study of supermode-density-wave-polariton condensation in a multimode cavity, advancing understanding of dissipative quantum phase transitions.

Findings

Observation of supermode-density-wave-polariton condensation

Demonstration of multimode cavity physics beyond mean-field

Potential for exploring nontrivial phase transitions and neuromorphic systems

Abstract

Phase transitions, where observable properties of a many-body system change discontinuously, can occur in both open and closed systems. Ultracold atoms have provided an exemplary model system to demonstrate the physics of closed-system phase transitions, confirming many theoretical models and results. Our understanding of dissipative phase transitions in quantum systems is less developed, and experiments that probe this physics even less so. By placing cold atoms in optical cavities, and inducing strong coupling between light and excitations of the atoms, one can experimentally study phase transitions of open quantum systems. Here we observe and study a novel form of nonequilibrium phase transition, the condensation of supermode-density-wave-polaritons. These polaritons are formed from a hybrid "supermode" of cavity photons coupled to atomic density waves of a quantum gas. Because the cavity supports multiple photon spatial modes, and because the matter-light coupling can be comparable to the energy splitting of these modes, the composition of the supermode polariton is changed by the matter-light coupling upon condensation. These results, found in the few-mode-degenerate cavity regime, demonstrate the potential of fully multimode cavities to exhibit physics beyond mean-field theories. Such systems will provide experimental access to nontrivial phase transitions in driven dissipative quantum systems as well as enabling the studies of novel non-equilibrium spin glasses and neuromorphic computation.