Soliton bunching in annular Josephson junction

Numerical simulations have been performed for an annular Josephson junction with a normalized length equal to 6, using the perturbed sine-Gordon equation. The calculated current-voltage characteristics reveal a small jump on the steps 3 and 4 in accordance with experimental observations. The computer simulations show that the jumps are caused by a transition from a non-bunched to a bunched fluxon oscillation state as the bias current is increased.