PERSISTENT PHOTOINDUCED SUPERCONDUCTIVITY

We review work done at UCSD on persistent photoconductivity and photoi nduced superconductivity in REBa2Cu3Ox thin films. It is shown that th e resistivity, Hall coefficient and c-axis parameter change significan tly upon illumination. All these effects require the presence of oxyge n vacancies, The maximum enhancement of the conductivity with illumina tion occurs for fully deoxygenated samples (x=6.0). The spectral depen dence of the persistent photoconductivity has a pronounced peak in the UV region at approximate to 4.1 eV. All these observations can be und erstood qualitatively with a model based on the trapping of photoexcit ed electrons at oxygen vacancies in the Cu-O chains of REBa2Cu3Ox.