Experimental analysis of the phase dynamics in small parallel arrays of Josephson junctions

We analyze Fiske resonances of one-dimensional parallel arrays of underdamped Josephson tunnel junctions. They appear in the current voltage (I-V) characteristics as resonant current singularities (steps) at finite 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 characteristics of the arrays exhibit three, five, and eight resonant current 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 applied magnetic flux are performed. The results of the simulation reproduce the experimentally observed features. (C) 1997 American Institute of Physics.