Kinetics of LBS rings

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We report on the measurements of the kinetics of expanding and collapsing rings in the exciton emission pattern. The rings are found to preserve their integrity during expansion and collapse, indicating that the observed kinetics is controlled by charge carrier transport rather than by a much faster process of exciton production and decay. The relation between ring kinetics and carrier transport, revealed by our experiment and confirmed by comparison with a theoretical model, is used to determine electron and hole transport characteristics in a contactless fashion.

Sen Yang, L. V. Butov, L. S. Levitov, B. D. Simons, A. C. Gossard, Kinetics of exciton emission patterns and carrier transport, arXiv:0908.2978v1 (2009).

Spatial shrinkage of exciton cloud at "localized bright spots"
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Spatial shrinkage of exciton cloud at "localized bright spots" ("anomalous traps") with reducing temperature leads to formation of a degenerate exciton gas

L.V. Butov, C.W. Lai, A.L. Ivanov, A.C. Gossard, and D.S. Chemla, Towards Bose-Einstein condensation of excitons in potential traps, Nature 417, 47 (2002).

L.V. Butov, A.C. Gossard, and D.S. Chemla, Macroscopically ordered state in an exciton system, cond-mat/0204482 April 22, 2002; Nature 418, 751 (2002)

L.V. Butov, L.S. Levitov, A.V. Mintsev, B.D. Simons, A.C. Gossard, and D.S. Chemla, Formation mechanism and low-temperature instability of exciton rings, cond-mat/0308117; Phys. Rev. Lett. 92, 117404 (2004)