Spontaneous Pattern Formation in a Polariton Condensate
  Polariton condensation can be regarded as a self-organization phenomenon, where phase ordering is established among particles in the system. In such condensed systems, further ordering can possibly occur in the particle density distribution, under particular experimental conditions. In this work we report on spontaneous pattern formation in a polariton condensate under non-resonant optical pumping. The slightly elliptical ring-shaped excitation laser we employ is such to force condensation to occur in a single-energy state with periodic boundary conditions, giving rise to a multi-lobe standing wave patterned state. 
F. Manni, K. G. Lagoudakis, T. C. H. Liew, R. Andr\'e, B.   Deveaud-Pl\'edran
cond-mat.quant-gas