Extrinsic origins of electrical transport anomalies near the superconducting transition in mesoscopic aluminum lines

We investigate whether inadvertent noise currents may induce the previously reported resistive peak and negative differential resistance (dV/dI) anomalies near the superconducting transition in quasi-one-dimensional aluminum lines. Although our samples show no intrinsic anomalies, low frequency current deliberately applied to the sample in addition to the ordinary measuring current induces the anomalies. In our work the resistive peak results from simple mixing, but the negative dV/dI feature arises from a more complex effect. (C) 1998 American Institute of Physics. [S0021-8979(98)07503-3].