Double sine-Gordon fluxons in isolated long Josephson junctions

A quantum flux, a 2 pi fluxon, described by a sine-Gordon equation is an el ementary excitation in long Josephson junctions. We investigated the fluxon dynamics in isolated long Josephson junctions. In such isolated systems, t he total number of Cooper pairs is conserved, so the fluxon dynamics map ch ange. We found that the fluxons obey a double sine-Gordon (DSG) equation ba sed on this change in the Josephson acceleration relation, i.e., the voltag e-phase difference relation. It should be possible to confirm the existence of DSG fluxons by detecting the relative oscillations of two pi fluxons. ( C) 2000 Elsevier Science B.V. All rights reserved.