Critical Currents of Superconducting Wide Bridges

Abstract

The temperature T and perpendicular magnetic field H dependences of the critical current I_c have been measured for superconducting wide bridges made of granular aluminum. The measured T dependence of I_c near the transition temperature T_c deviates from that derived from the Ginzburg-Landau (GL) equations in a uniform current distribution. The deviation occurs even under the condition that the self-magnetic field due to the current is negligible, and it increases as the width of bridge or the coherence length increases. These results show that the pair-breaking current density j_c at the edge of bridge is enhanced from j_c^GL owing to current concentration due to its geometry. The peak structure with clear hysteresis for the sweep of H was observed in the I_c-H characteristics. The width of the peak seems to be inversely proportional to the bridge width.