Flux quantization in stationary and nonstationary states in long Josephsonjunctions

Dynamical chaos and the stability of states in long Josephson junctions are investigated from the standpoint of flux quantization. It is shown that th e stationary Meissner and fluxon states having integer numbers of fluxons a re stable. Stationary antifluxon states also having integer numbers of flux quanta and all other states with half-integer numbers of flux quanta are u nstable. Transitions between all states - Meissner states and states having integer and half-integer numbers of flux quanta - take place in the nonsta tionary case, and all these states are dynamically equivalent, but the numb er of flux quanta is an irregular time-dependent function for the chaotic s tates and a regular one for the regular states. (C) 2000 American Institute of Physics. [S1063-777X(00)00211-5].