Microwave-induced dc voltages in BaPb1-xBixO3 bicrystal Josephson junctions

We have fabricated an artificial BaPb1-xBixO3 grain boundary tunnel junction on a SrTiO3 bicrystal substrate. Current-voltage characteristics exhibit supercurrent and quasi-particle tunneling which is commonly observed for superconductor-insulator-superconductor (SIS) type junctions. A Shapiro step is observed for a junction with a large area under microwave radiation. On the other hand, microwave-induced dc voltages at zero bias current are observed for a narrow junction. This dependence on the junction width indicates that generation of the microwave-induced voltages is related to normal resistance or capacitance of a junction.