Bunching of fluxons in a long Josephson junction with surface losses.

Abstract

It is known that the sine-Gordon model of a long Josephson junction with a surface-loss term predicts a spatially oscillating trailing tail of a strongly contracted fluxon. In the present work, it is demonstrated that this should give rise to bunched (bound) states of fluxons, although the onset of the bunching drastically differs from the standard situation recently investigated in terms of the perturbed nonlinear Schro\ifmmode\ddot\else\textasciidieresis\fi{}dinger model. Influence of the bunching on the I-V characteristic of an annular junction with a finite number of trapped fluxons is analyzed qualitatively. It is demonstrated that the bunching may set in with a small hysteresis, and it increases voltage at a given current. The latter effect has been observed in most recent experiments with the annular junction.