Manifestation of collective properties of spatially indirect excitons in GaAs/AlGaAs asymmetric double quantum wells

Low-temperature (T=1.8, 4.2 K) luminescence of GaAs/Al_0.3Ga_0.7As double-coupled asymmetric quantum wells (DQW) is observed under variation of an electric field V _dc applied along the normal to the DQW plane. The FWHM of the indirect exciton (IX) emission line was found to undergo, within a certain interval of V _dc, a strong (up to a factor 3.5) narrowing, accompanied by anomalously large IX intensity fluctuations in time within the V _dc region where a strong decrease (or increase) of the FWHM is observed to occur. The dependence of the FWHM on the pumping level I _p also exhibits a substantial decrease of the FWHM within a certain I _p interval. The results obtained are discussed in the frame of an assumption which relates the observed phenomena to the onset of a condensed state in the interacting ensemble of spatially indirect excitons in DQWs. Fiz. Tverd. Tela (St. Petersburg) 41, 325–329 (February 1999)