Interfacial resistive anomaly at a normal-superconducting boundary

We have observed an anomalous peak ({~}5% of the normal-state resistance) in the resistive transition of a thin-film aluminum system consisting of regions of different, but comparable, transition temperatures. The peak occurs at slightly above the transition temperature of the lower Tc section. The magnitude decreases with the distance of the voltage probes from the normal-superconducting (N-S) interface with a characteristic length scale of a few {μ}m and is sensitive to a magnetic field. This anomaly appears to be consistent with a nearly constant superconducting potential near a N-S interface.