Photovoltaic effect in small superconducting-normal-metal systems

We have observed an unusual photovoltaic effect in small metallic systems in which some portion of the sample is superconducting. In these systems, an applied microwave field can induce a de voltage (the ''photovoltage''), V-dc. We have found that this voltage can be an antisymmetric function of magnetic field, i.e., V-dc(+ H) = - V-dc(- H) It also exhibits aperiodic fluctuations as a function of both H, and the strength of the microwave field. Results for several different sample geometries suggest that it is due to the inverse Josephson effect, although the samples are not obviously reminiscent of weak link structures.