Abstract:
:During the past ten years, coupled quantum wells have emerged as a promising system for experiments on Bose condensation of excitons, with numerous theoretical and experimental studies aimed at the demonstration of this effect. One of the issues driving these studies is the possibility of long-range coherent transport of excitons. Excitons in quantum wells typically diffuse only a few micrometres from the spot where they are generated by a laser pulse; their diffusion is limited by their lifetime (typically a few nanoseconds) and by scattering due to disorder in the well structure. Here we report photoluminescence measurements of InGaAs quantum wells and the observation of an effect by which luminescence from excitons appears hundreds of micrometres away from the laser excitation spot. This luminescence appears as a ring around the laser spot; almost none appears in the region between the laser spot and the ring. This implies that the excitons must travel in a dark state until they reach some critical distance, at which they collectively revert to luminescing states. It is unclear whether this effect is related to macroscopic coherence caused by Bose condensation of excitons.
journal_name
Naturejournal_title
Natureauthors
Snoke D,Denev S,Liu Y,Pfeiffer L,West Kdoi
10.1038/nature00940keywords:
subject
Has Abstractpub_date
2002-08-15 00:00:00pages
754-7issue
6899eissn
0028-0836issn
1476-4687pii
nature00940journal_volume
418pub_type
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