Origin of the inner ring in photoluminescence patterns of quantum well excitons A. L. Ivanov, L. E. Smallwood, A. T. Hammack, Sen Yang, L. V. Butov and A. C. Gossard Europhys. Lett., 73 6 (2006) 920-926 Published online: 15 February 2006 DOI: 10.1209/epl/i2006-10002-4