A quantum dot ratchet: Experiment and theory H. Linke, W. Sheng, A. Löfgren, Hongqi Xu, P. Omling and P. E. Lindelof Europhys. Lett., 44 3 (1998) 341-347 Published online: 01 September 2002 DOI: 10.1209/epl/i1998-00562-1