The anomaly of current-voltage characteristics of a mesoscopic aluminum line

The I-V characteristics of mesoscopic aluminum wire have been studied. Step structures are found near superconducting transition temperature and the number of the steps is different at different temperature. At lower temperatures, the steps gradually turn into strong peaks. These anomalous features can be suppressed by a magnetic field. We propose an interpretation based on the nonequilibrium superconductivity due to the formation of phase slip centers (PSCs). The PSCs are excited one by one with increasing of current and the interaction between them will affect the charge imbalance length, leading to the anomalous peaks in the I-V characteristics near the critical current.