EXPERIMENTAL-ANALYSIS OF THE PHASE DYNAMICS IN SMALL PARALLEL ARRAYS OF JOSEPHSON-JUNCTIONS

We analyze Fiske resonances of one-dimensional parallel arrays of unde rdamped Josephson tunnel junctions. They appear in the current voltage (I-V) characteristics as resonant current singularities (steps) at fi nite voltages V-m when a magnetic field H is applied perpendicular to the array cells. We present measurements of current step amplitudes I- cm, and of the maximum Josephson current I-c0 as a function of H, for arrays made of four, six, and ten small Josephson junctions. The I-V c haracteristics of the arrays exhibit three, five, and eight resonant c urrent steps, respectively, at increasing voltages. In all devices we find that the current amplitude of the highest order step has just one maximum occurring at H approximate to 1/2H, being H* the first field value where I-c0(H) approximate to I-c0(0). Numerical simulations of the phase dynamics in small parallel arrays as a function of the appl ied magnetic flux are performed. The results of the simulation reprodu ce the experimentally observed features. (C) 1997 American Institute o f Physics.