Quantized Vortices and Four-Component Superfluidity of Semiconductor   Excitons
  We study spatially indirect excitons of GaAs quantum wells, confined in a 10 microns electrostatic trap. Below a critical temperature of about 1 Kelvin, we detect macroscopic spatial coherence and quantised vortices in the weak photoluminescence emitted from the trap. These quantum signatures are restricted to a narrow range of density, in a dilute regime. They manifest the formation of a four-component superfluid, made by a low population of optically bright excitons coherently coupled to a dominant fraction of optically dark excitons. 
Romain Anankine, Mussie Beian, Suzanne Dang, Mathieu Alloing, Edmond   Cambril, Kamel Merghem, Carmen Gomez Carbonell, Arist...
cond-mat.quant-gas