Experiments on soliton motion in annular Josephson junctions

We report here the results of an extensive experimental investigation of soliton dynamics in Josephson junctions of different annular geometries. The annular geometry is unique in that it allows for the study of undisturbed soliton motion as well as soliton–antisoliton collisons, since there are no boundary effects. We have successfully trapped a single soliton in an annular junction and found good agreement with perturbation theory at low soliton velocity, and evidence of departure from perturbation theory at higher velocity. We also discuss the observation of fine structure on the I-V curve for a single trapped soliton, and evidence linking the stability of the soliton to surface damping.