Observation of macroscopic coherence in self-organized dipolar excitons
  We report experiments showing that spatially indirect excitons confined in a wide single quantum well can exhibit macroscopic spatial coherence. Extended coherence is spontaneously established in the regime where indirect excitons form a distinctive ring shaped pattern fragmented into microscopic beads. These contain a large concentration of indirect excitons at sub-Kelvin temperatures, the excitons spatial coherence being the greatest in the vicinity of the fragments. 
M. Alloing, D. Fuster, Y. Gonzalez, L. Gonzalez, F. Dubin
cond-mat.mes-hall