RESISTANCE ANOMALY AND EXCESS VOLTAGE NEAR SUPERCONDUCTING INTERFACES

We present resistance and current-voltage characteristics of an alumin um film with two regions of different superconducting transition tempe ratures. The voltage and hence resistance increase above normal state values near the transition. The excess voltage disappears with increas ing bias current, accompanied by negative differential resistances. Th is behavior is associated with the charge imbalance that accompanies n ormal-superconducting interfaces and phase slip centers.