Ac-induced thermal vortex escape in magnetic-field-embedded long annular Josephson junctions

Abstract

We investigate theoretically the thermal escape behavior of trapped magnetic fluxons in long annular Josephson junctions in dc magnetic fields, and perturbed by a probing ac current. The study is motivated by recently published experimental data that show multipeaked escape distributions for increasing bias current in the extreme low temperature regime when the system is perturbed by an ac current. We demonstrate that the observed behavior of multipeaked escape distributions can be reproduced and predicted in the entirely classical, thermally driven sine-Gordon model, which is widely accepted as accurately describing the experimental system. We interpret the observed multipeaked distributions as being directly induced by dynamical resonances between the applied ac perturbation and the natural oscillation frequency of a trapped fluxon.