Soliton Chains in Annular Josephson Junctions: Experiments

We report for the first time the trapping of several solitons (flux quanta) in annular Josephson junctions. We have realized experimentally two different techniques for the magnetic flux trapping in the junctions. First, using low temperature scanning electron microscopy (LTSEM) we applied the electron beam producing a local heating of the top superconducting film and trapped one by one several magnetic flux quanta in the tunnel barrier area of the Josephson junction. Second, by applying the external monopole-like magnetic field by means of a special coil we were also able to trap the flux in the junction at temperatures near the critical temperature of the superconducting electrodes. We have studied the I-V curves of the junction with several trapped solitons and compared the velocity of the soliton chain with one soliton velocity and the perturbation theory. We link the deviations of the soliton chain velocity from the one soliton velocity with the effects of the interaction between solitons and their bunching at high velocity.