Study of excitonic superfluidity in Cu/sub 2/O

Summary form only given. The recent observation of Bose-Einstein condensation (BEG) in ultracold atoms has stirred a considerable renewal of interest for this effect. A gas of excitons or biexcitons in semiconductors provides another system where BEC has been observed. A particularly interesting aspect of an excitonic Bose-Einstein condensate concerns its propagation in the form of a superfluid. Excitonic superfluidity corresponds to a drag-free, wavelike flow of electronic excitation energy through a crystal. Experimental evidence for superfluidity of excitons in Cu/sub 2/O is presented.