DEVIL STAIRCASE DYNAMIC IN ARRAYS OF OVERDAMPED JOSEPHSON-JUNCTIONS

The domains of dynamical coherence (i.e. the Shapiro step-plateaus) ob servable when an array of overdamped Josephson junctions is subjected to an external periodic perturbation, can be strongly modified by the presence of both the disorder and the frustration, f. In particular, b y varying the value of f it is possible to induce a reduction in the w idth of the integer giant Shapiro step-plateaus (corresponding to a co mpression of the attraction basin of the main locked states of the sys tem) and the progressive appearance of a subharmonic devil staircase c haracterized by a fractal dimension, D = 0.88, value that agrees with what has been observed for other complex systems. The sensitivity of t he I-V characteristics to f is mirrored in the complexity of the dynam ical phase space composed by phase-locked domains separated by regions of chaotic dynamics.