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 ${\mathit{T}}_{\mathit{c}}$ 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 μm and is sensitive to a magnetic field. This anomaly appears to be consistent with a nearly constant superconducting potential near a N-S interface.