Numerical simulations of Fiske steps in intrinsic Jospehson junctions

We have numerically investigated the vortex dynamics in a stack of intrinsic Josephson junctions (IJJs) having length L=5λJL=5λJ. We performed simulations by using the perturbed, coupled sine-Gordon model taking into account thermal fluctuations. In the absence of thermal fluctuations, the current–voltage characteristics show a series of smaller amplitude Fiske steps corresponding to different cavity modes, excited by the collective vortex-flow depending on an external magnetic field. However, in the presence of thermal fluctuations, we found that only Fiske steps corresponding to the lowest-velocity cavity mode appear clearly and others becomes indistinct. This suggests that the out-of-phase mode becomes more stable than other modes due to the fluctuations. In addition, the stable steps show a field dependence similar to the Fiske steps in single junction. The results are consistent with recent experimental observations in IJJs in the vortex-flow state.