Mode-locking and dynamical correlation effects in a driven Josephson junction network

Mode-locking phenomena in a Josephson junction network (JJN) driven by both dc and ac currents are studied using a numerical simulation. We consider a ladder type of structure of the JJN, i.e., Josephson junction ladder (JJL). Under a random magnetic field, it is found that the mode locking exists in the present system, and mode-locked steps are observed in the dc current-voltage characteristics. Outside the steps, due to the effect of the random field, plastic deformation of phase-phase coupling occurs, and then there appears plastic flow. As the bias current is increased further, transition from the plastic to elastic flow state occurs. Around the transition point, a critical behavior of the voltage-voltage correlation is observed. We discuss the peculiar nature of the mode-locking phenomena in the JJL.