Controlled Polarization Switch in a Polariton Josephson Junction

Abstract: The interaction between a particle's spin and momentum -- known as spin-orbit (SO) coupling -- is the cornerstone of modern spintronics. In Bose-Einsten condensates of ultracold atoms, SO coupling can be implemented and precisely controlled experimentally; photonic systems, on the other hand, possess an intrinsic SO interaction due to the longitudinal-transverse splitting of the photon modes. In this work, we focus on such spinor, SO-coupled exciton-polariton condensates on a ring, where the strength of the synthetic magnetic field is controlled by the geometrical dimensions of the structure. Inspired by recent experiments, we investigate the dynamics of a weakly-nonlinear four-mode bosonic Josephson junction within this geometry. We discover a narrow parameter range in which the interplay of the tunneling dynamics with polariton-specific SO coupling leads to a new regime, with dynamical switching of the fluid's circular polarization degree to the opposite, along the entire ring or on just one of its halves. Our results demonstrate polariton condensates in ring configurations as excellent candidates for all-optical controllable spin-switch applications, with prospects for scalability and observing non-trivial polarization patterns.