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Phys. Rev. Lett. 97, 187402 (2006) [4 pages]

Coherence Length of Cold Exciton Gases in Coupled Quantum Wells

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Sen Yang, A. T. Hammack, M. M. Fogler, and L. V. Butov
Department of Physics, University of California at San Diego, La Jolla, California 92093-0319, USA

A. C. Gossard
Materials Department, University of California at Santa Barbara, Santa Barbara, California 93106-5050, USA

Received 27 June 2006; published 31 October 2006

A Mach-Zehnder interferometer with spatial and spectral resolution was used to probe spontaneous coherence in cold exciton gases, which are implemented experimentally in the ring of indirect excitons in coupled quantum wells. A strong enhancement of the exciton coherence length is observed at temperatures below a few Kelvin. The increase of the coherence length is correlated with the macroscopic spatial ordering of excitons. The coherence length at the lowest temperature corresponds to a very narrow spread of the exciton momentum distribution, much smaller than that for a classical exciton gas.

© 2006 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.97.187402
DOI:
10.1103/PhysRevLett.97.187402
PACS:
78.67.De, 71.35.−y, 73.21.Fg