Photodoping of YBaCuO Grain Boundary Josephson Junctions

coupling. In these GBJJ, the grain boundary which Since the discovery of High Tc Superconductivity constitutes the barrier is a weak superconducting at the end of 1986 [1], great attention has been paid region which is oxygen deficient andyor disordered. to the investigation of the action of light on High Tc Then, illumination of such junctions will change the Superconductors (HTSC). Besides their high trantransport properties of the oxygen deficient barrier sition temperature, the HTSC show unusual physical like in the thin films and thus change the Josephson properties. Some of these are persistent photoconduccoupling. The PPS will result in a dc Josephson curtivity (PPC) and persistent photoinduced superconrent increased and the voltage positions of the Fiske ductivity (PPS). The superconducting properties of resonances (ac Josephson properties) shifted. The an oxygen deficient superconducting YBa2Cu3Ox thin PPC will induce a decrease of the normal state resistfilm increase with illumination and persist after the ance of the junction. light is switched off if the sample is kept at low tem-