Abstract
We investigate theoretically the V-I characteristics and voltage noise of superconducting tunnel junctions with a small critical current via the matrix-continued-fraction method. Special attention is paid to the large hysteresis in the V-I characteristics and to the voltage-noise anomaly observed in preliminary experiments.
The current dependence of the voltage noise shows a strong asymmetry between the forward and the backward current ramping and a discontinuous change in the noise close to its measured maximum occurring at the switching current. We show that both the large hysteresis and the voltage noise anomaly in this current-biased setup are a consequence of the influence of the junction's electromagnetic environment.
Typically, the voltage-noise dependence on the junction current parametrized by the external drive contains a loop that is, however, not observed experimentally because of the implementation of the junction-current ramp. Skipping a part of the loop is responsible for the observed hysteresis as well as the noise anomaly.