PHOTOVOLTAIC SIGNALS IN YBA2CU3O7-DELTA FILMS DUE TO LASER-INDUCED MAGNETIC-FLUX REDISTRIBUTION

A Voltaic response upon pulsed laser irradiation was obtained from sup erconducting epitaxial YBa2Cu3O7-delta films subjected to non-static m agnetic fields. A model is proposed which relates the voltaic signals to a laser-induced change of the shielding currents within the sample. Experiments are described which, in combination with this model, allo w one to investigate the decay of shielding currents, to observe estab lishment of the critical state and to estimate critical currents j(c)( B, T). From the decay of the shielding currents, activation energies U (B, T) can be deduced by standard analysis. Scanning of the laser spot across the films gives information on the local distribution of nux-d ensity gradients.