Quantum droplets and condensates in an optical lattice coupled to a dissipative cavity: Collective excitations and nonequilibrium dynamics
Phys. Rev. A 114, 053313 – Published 9 November, 2026
DOI: https://doi.org/10.1103/8rxt-d65j
Abstract
Motivated by recent experiments on light-matter interacting systems, we investigate a dilute Bose gas and self-bound quantum droplets in a one-dimensional optical lattice coupled to a lossy cavity mode. Using a classical-field approach, we determine the stationary states and collective excitations of this nonequilibrium system. Apart from the usual Bogoliubov modes, we identify a polaritonlike gapped excitation, the frequency of which softens as a precursor of the density ordering transition. Moreover, its relaxation time diverges as the critical point is approached, signaling the nonequilibrium nature of this transition. Dynamically, this polaritonlike mode can be probed by inducing cavity field fluctuations, which in turn generates spatiotemporal oscillations of both the condensate and droplet states. In the droplet regime, we also analyze the bound modes which bear the characteristics of such nonequilibrium self-bound state. In addition, we uncover solitonic nonequilibrium states, including condensate with kinklike configuration and double-droplet state, and investigate their robustness following a sudden quench. Remarkably, although these states become unstable beyond a critical coupling, they continue to manifest in the dynamics, akin to the scarring phenomena. Our results demonstrate that dissipative cavity coupling provides a versatile route for exploring rich nonequilibrium dynamics of condensates and quantum droplets within experimentally accessible settings.
