Electrodynamic duality and vortex unbinding in driven-dissipative condensates
We investigate the superfluid properties of two-dimensional driven Bose liquids, such as polariton condensates, using their long-wavelength description in terms of a compact Kardar-Parisi-Zhang (KPZ) equation for the phase dynamics. We account for topological defects (vortices) in the phase field through a duality mapping between the compact KPZ equation and a theory of non-linear electrodynamics coupled to charges. Using the dual theory we derive renormalization group equations that describe vortex unbinding in these media. When the non-equilibirum drive is turned off, the KPZ non-linearity λ vanishes and the RG flow gives the usual Kosterlitz-Thouless (KT) transition. On the other hand, with non-linearity λ > 0 vortices always unbind, even if the same system with λ = 0 is superfluid. We predict the finite size scaling behavior of the superfluid stiffness in the crossover governed by vortex unbinding showing its clear distinction from the scaling associated with the KT transition.