Anticorrelation between temperature and fluctuations of the switching current in moderately damped Josephson junctions

We study the influence of dissipation on the switching current statistics of moderately damped Josephson junctions. Different types of both low- and high-Tc junctions with controlled damping are studied. The damping parameter of the junctions is tuned in a wide range by changing temperature, magnetic field, and gate voltage and introducing a ferromagnetic layer or in situ capacitive shunting. A paradoxical collapse of switching current fluctuations with increasing T occurs in all studied junctions. The phenomenon critically depends on dissipation in the junction and is explained by the interplay of two counteracting consequences of thermal fluctuations, which, on one hand, assist in premature switching into the resistive state and, on the other hand, help in retrapping back to the superconducting state. This is one of the rare examples of anticorrelation between temperature and the amplitude of fluctuations of a physically measurable quantity.