Origin of the inner ring in photoluminescence patterns of quantum well excitonsA. L. Ivanov, L. E. Smallwood, A. T. Hammack, Sen Yang, L. V. Butov and A. C. GossardEurophys. Lett., 73 6 (2006) 920-926DOI: https://doi.org/10.1209/epl/i2006-10002-4