Transition to a Bose-Einstein condensate and relaxation explosion of excitons at sub-Kelvin temperatures
Abstract
Quasiparticles in quantum many-body systems have essential roles in modern physical problems. Bose-Einstein condensation (BEC) of excitons in semiconductors is one of the unobserved quantum statistical phenomena predicted in the photoexcited quasiparticles in many-body electrons. In particular, para-excitons in cuprous oxide have been studied for decades because the decoupling from the radiation field makes the coherent ensemble a purely matter-like wave. However, BEC has turned out to be hard to realize at superfluid liquid helium-4 temperatures due to a two-body inelastic collision process. It is therefore essential to set a lower critical density by further lowering the exciton temperature. Here we cool excitons to sub-Kelvin temperature and spatially confine them to realize the critical number for BEC. We show that BEC manifests itself as a relaxation explosion as has been discussed in atomic hydrogen. The results indicate that dilute excitons are purely bosonic and BEC indeed occurs.
- Publication:
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Nature Communications
- Pub Date:
- May 2011
- DOI:
- 10.1038/ncomms1335
- arXiv:
- arXiv:1008.2431
- Bibcode:
- 2011NatCo...2..328Y
- Keywords:
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- Condensed Matter - Quantum Gases
- E-Print:
- 19 pages, 3 figures, Supplementary Information (12 pages, 4 figures) included