VORTEX-INDUCED RECTIFICATION IN TYPE-II SUPERCONDUCTORS

We report a large rectification effect in superconducting films in a parallel 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 currents, and beyond I-c, the magnitude of the voltage is different for positive and negative currents, \V(+I)\ not equal \V(-I)\. Furthermore, the critical current difference \I-c+\ - \I-c-\ shows complicated behavior, changing sign as temperature and magnetic field are varied. We discuss a model based on the Bean-Livingston surface barrier and inhomogeneous bulk pinning that accounts for all observed behavior.