Quantum fluids of light in all-optical scatterer lattices

Semiconductor microcavities allow engineering of artificial lattices with optical write-in and read-out of information. Here, the authors show an optically imprinted system of exciton-polaritons arranged in a Lieb lattice and reveal a nonequilibrium transition from scattered- to trapped polariton condensates. One of the recently established paradigms in condensed matter physics is examining a system's behaviour in artificial potentials, giving insight into phenomena of quantum fluids in hard-to-reach settings. A prominent example is the matter-wave scatterer lattice, where high energy matter waves undergo transmission and reflection through narrow width barriers leading to stringent phase matching conditions with lattice band formation. In contrast to evanescently coupled lattice sites, the realisation of a scatterer lattice for macroscopic matter-wave fluids has remained elusive. Here, we implement a system of exciton-polariton condensates in a non-Hermitian Lieb lattice of scatterer potentials. By fine tuning the lattice parameters, we reveal a nonequilibrium phase transition between distinct regimes of polariton condensation: a scatterer lattice of gain guided polaritons condensing on the lattice potential maxima, and trapped polaritons condensing in the potential minima. Our results pave the way towards unexplored physics of non-Hermitian fluids in non-stationary mixtures of confined and freely expanding waves.

Automated summary

This study explores the optical manipulation of exciton-polariton systems in Lieb lattices, revealing a nonequilibrium phase transition between scatterer lattice and trapped polariton condensates. By fine tuning lattice parameters, the researchers demonstrate the behavior of polaritons condensing in different potential regimes, paving the way for further exploration of non-Hermitian fluids in non-stationary mixtures.