Skewness variations of switching-current distributions in moderately damped Josephson junctions due to thermally induced multiple escape and retrapping

Abstract

A crossover at a temperature T* in the temperature dependence of the width σ of the distribution of switching currents of moderately damped Josephson junctions has been reported in a number of recent publications. For T < T*, dσ/dT is positive and the IV characteristics are associated with underdamped behaviour; for T > T*, dσ/dT is negative and the IV characteristics resemble overdamped behaviour. We have investigated in detail the behaviour of Josephson junctions around T* by using Monte Carlo simulations including retrapping from the running state into the supercurrent state as given by a model due to Ben-Jacob et al. Thermally induced multiple escape and retrapping events play an important role for moderate damping. Around T*, not just at lower T < T*, the shape of the distribution and σ(T) are largely determined by the shape of the conventional underdamped thermally activated switching distribution. The behaviour is more fully understood by considering two crossover temperatures. The skewness of the switching distribution parametrises its shape and becomes less negative, then positive, as T increases above the lower crossover temperature.