Collective motion of Josephson vortex lattice in long stacked junction fabricated from Bi-2212 whisker

We study the I-V characteristics of long Bi-2212 stacked junctions in the Josephson flux-flow regime in parallel magnetic field (B parallel tob). We measure both voltage position of the flux-flow step, V-ff, corresponding to the maximum velocity of Josephson vortex lattice, and the flux-flow resistivity, rho (ff), as a function of magnetic field B = 0.1-4 T. We found plateau-like features of constant V-ff on dependence V-ff (B) corresponding to washboard frequencies 600 GHz and 3 THz. We discuss these features as mode locking of washboard frequency with active intrinsic modes of the stack. We found also that field dependence of flux-flow resistivity can be well described by a recent model [A. Koshelev, Phys. Rev. B 62 (2000) R3616] which takes into account both out-of-plane and in-plane dissipation. (C) 2001 Elsevier Science B.V. All rights reserved.