EFFECT OF CURRENT DIRECTION ON THE DYNAMICS OF JOSEPHSON-JUNCTION ARRAYS

We present an extensive experimental and theoretical study of the effect that the current direction has on the dynamical properties of rf and dc current-biased overdamped Josephson-junction arrays. We show that a strong spatial symmetry of the array about the direction of the macroscopic current flow is necessary for arrays to show only integer giant Shapiro steps. If this symmetry is broken, arrays will produce both fractional and integer giant Shapiro steps. A moving-vortex model and a pendulum model are used to describe our experimental and computational results.