Soliton dynamics in Josephson tunnel junctions

The non-linear dynamics of Josephson junctions is well described by the perturbed sine-Gordon equation together with the appropriate boundary conditions. A possible solution of the pure sine-Gordon equation are solitons. In the junction the (quasi) solitons manifest themselves as Josephson vortices, each of them carrying one magnetic flux quantum. We used the technique of Low Temperature Scanning Electron Microscopy to study the soliton dynamics in superconducting tunnel junctions of various geometries. The electron beam power can be adjusted to work in different regimes. For high power, the beam acts as an active probe and we were able to introduce individual solitons in annular junctions one by one and studied multisoliton behavior without the influence of boundaries. For low power, the beam acts as a passive probe influencing the soliton dynamics in a well controlled way. Here, we investigated details of the dynamic soliton behavior.