Vortex dynamics in Josephson ladders with π-junctions

Both experimental and numerical studies of a self-frustrated triangular array of π-junctions are reported. The array of SFS Josephson junctions shows a transition to the π-state and self-frustration with a decrease in temperature. This manifests itself in a half-period shift of the bias critical current versus applied magnetic field. At temperatures close to the 0–π transition this dependence shows a doubling of its periodicity frequency that can be explained by 0–π bistability of the SFS junctions. The change in the array behaviour with number of unit cells has been studied by means of numerical simulation.