Phase locked fluxon-antifluxon states in stacked Josephson junctions

Measurements were made on a two-stack long Josephson junction with very similar parameters and electrical access to the thin middle electrode. Mutually phase-locked fluxon-antifluxon states were observed. The observed propagation velocity is in agreement with the theoretical prediction. The I-V curves recorded using the bias current in one of the junctions as fixed parameter show that these states continue to also exist when the other junction is oppositely biased. This is found in numerical simulations based on the experimental junction parameters as well. We propose a model in which waves in the junctions coexist with fluxons. (C) 1996 American Institute of Physics.