Experimental investigation of the magnetic behavior of superconducting-normal-superconducting Josephson junctions

We have measured the magnetic field dependence of the supercurrent in micron-size medium and high current density superconducting-normal-superconducting Nb–Au–Nb Josephson junctions. We find good quantitative agreement between the experiment and a theory for the distributed Josephson effect in such junctions. For finite bias voltages, high current density junctions show a monotonic decrease in the effective critical current with increasing field in sharp contrast to the resistively shunted junction model which predicts the well-known Fresnel-type behavior. Our medium current density junctions represent an intermediate case, residual Fresnel behavior is observed at small bias voltages, but a monotonic decrease with the field is observed for higher bias voltages.