VORTEX-INDUCED RECTIFICATION IN TYPE-II SUPERCONDUCTORS

We report a large rectification effect in superconducting films in a p arallel magnetic field. This rectification effect is manifested in two features in current-voltage characteristics: The critical current, I- c, is found to differ by as much as 40% for negative and positive curr ents, and beyond I-c, the magnitude of the voltage is different for po sitive and negative currents, \V(+I)\ not equal \V(-I)\. Furthermore, the critical current difference \I-c+\ - \I-c-\ shows complicated beha vior, changing sign as temperature and magnetic field are varied. We d iscuss a model based on the Bean-Livingston surface barrier and inhomo geneous bulk pinning that accounts for all observed behavior.