PERSISTENT PHOTOCONDUCTIVITY IN YBA2CU3O6-DOPING NEAR THE SEMICONDUCTOR-METAL TRANSITION(X FILMS AS A METHOD OF PHOTO)

Persistent photoconductivity and metastable photoinduced superconducti vity recently discovered by Kudinov et.al. in YBa2Cu3O6+x films are st udied over the oxygen content 0 < x < 1. As evidenced, prolonged illum ination of the films by visible light leads to essential enhancement o f their metallic and superconducting properties. The observed phenomen a are attributed to photoexcitation of additional mobile holes into Cu O2 planes (photodoping), allowing a metastable superconducting phase t o be initiated. It is suggested that photoinduced superconductivity ma y have applications in fabrication of in situ optically tunable weak-l ink devices.