PHOTOINDUCED CHANGES IN HIGH-TEMPERATURE SUPERCONDUCTING FILMS

Photoexcitation experiments performed in oxygen deficient but metallic YBa2Cu3Ox c-axis oriented films revealed that the persistent photoind uced enhancement of conductivity and superconductivity are not restric ted to the insulating side of the metal-insulator transition. A clear increase of the critical temperature T-c, which is accompanied by a de crease of the resistivity in the normal state rho(ab), is observed for all studied oxygen contents (6.4 less than or equal to x less than or equal to 6.6). In this oxygen content range, the persistent photoindu ced changes in T-c and rho(ab) have a strong dependence on the oxygen stoichiometry of the film. Several mechanisms which may explain the pe rsistent photoinduced phenomena are discussed.