Superconducting and normal-state properties of oxygen-deficient YBa2Cu3Ox thin films under light illumination

We report on the influence of light on the normal state and superconducting transport properties of superconducting YBa2Cu3O6.6 thin films. After illumination with white light for several hours at 150 Y a persistent decrease of the electrical resistivity, an increase of the Hall mobility and a change of the magnetoconductivity was observed. The effect relaxes with a time constant of several hours at 320 K. A kink in the resistivity curve and a sign change in the slope of the Hall effect at this temperature in nonilluminated samples have also been observed. Measurements of the fluctuation magnetoconductivity revealed a photoinduced enhancement of the superconducting coherence lengths in both in-plane and out-of-plane directions. Our results indicate structural rearrangements of oxygen vacancies in the Cu-O chains upon illumination.