Collective dynamics of Josephson vortices in intrinsic Josephson junctions: exploration of in-phase locked superradiant vortex flow states

In order to explore the "superradiant" condition for the moving Josephson v ortices in intrinsic Josephson junctions (IJJs), we perform large scale num erical simulations for the IJJs with realistic dimensions under a layer-par allel magnetic field (H > 1T). Three clear step-like structures, at which w e find structural transitions in moving flux-line lattice, are observed in the I-V curve. The flow states of the Josephson vortices are classified int o four regions, from I to IV, according to the applied current or voltage v alues. The superradiant state, in which moving Josephson vortices forms the in-phase rectangular lattice, is stabilized in region III. In the superrad iant state, the power spectra of excited electric fields show very sharp pe ak structures and the power at the peak position is very large. From the ei gen mode analysis, we show that the step-like structure in the I-V curve co rresponding to structural transitions in moving lattices originates from th e resonances between the transverse Josephson plasma modes and the motion o f the Josephson vortices. (C) 2000 Elsevier Science B.V. All rights reserve d.