Optical response of dark exciton Bose-Einstein condensate

Th. Östreich, T. Portengen, Lu Jeu Sham

Keith R. Burnett

Zai-Dong Li, Qiuyan Li

Romain Anankine, Suzanne Dang, Mussie Beian +5 more

Very recently, we have shown experimentally that Bose-Einstein condensation leads to a mostly dark gas of excitons in GaAs heterostructures. A small fraction of optically active states nevertheless contributes to the condensate so that a weak photoluminescence manifests the excitons non-classical spatial coherence. In this Letter, we show that this photoluminescence experiences a threshold increase of temporal coherence at the critical temperature for excitonic condensation.

Monique Combescot, M. G. Moore, Carlo Piermarocchi

We propose a mechanism for optical trapping of dark excitons by linearly polarized unabsorbed standing waves, with a potential depth of the order of a few meV. Since this trapping, based on carrier exchanges with virtual excitons coupled to unabsorbed photons, equally acts on bright and dark states, Bose-Einstein condensation of excitons--which occurs in dark states--must appear as dark spots in a cloud of bright excitons, at the trap potential minima, when the temperature decreases.

Eiichi Hanamura