Abstract:We study a four-component polariton system in the optical parametric oscillator regime consisting of exciton, photon, signal, and idler modes across the Berezinskii-Kosterlitz-Thouless (BKT) transition. We show that all four components share the same BKT critical point, and algebraic decay of spatial coherence with the same critical exponent. However, while the collective excitations in different components are strongly locked, both close to and far from criticality, the spontaneous creation of topological def… Show more
We develop a semi-analytical description for the Berezinskii-Kosterlitz-Thouless (BKT) like phase transition in nonequilibrium Bose-Einstein condensates. Our theoretical analysis is based on a noisy generalized Gross-Pitaevskii equation. Above a critical strength of the noise, spontaneous vortexantivortex pairs are generated. We provide a semi-analytical determination of the transition point based on a linearized Bogoliubov analysis, to which some nonlinear corrections are added. We present two different approaches that are in agreement with our numerical calculations in a wide range of system parameters. We find that for small losses and not too small energy relaxation, the critical point approaches that of the equilibrium BKT transition. Furthermore, we find that losses tend to stabilize the ordered phase: keeping the other parameters constant and increasing the losses leads to a higher critical noise strength for the spontaneous generation of vortex-antivortex pairs. Our theoretical analysis is relevant for experiments on microcavity polaritons.
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