JOSEPHSON-JUNCTION LADDER - A BENCHMARK FOR NONLINEAR CONCEPTS

The theoretical analysis of the ground state properties and dissipativ e dynamics of an anisotropic ladder of Josephson junctions has reveale d interesting features associated to the nonlinear character of the Jo sephson effect, combined with the inherent discreteness of the system and the peculiarities of the ladder geometry. We analyse some aspects of its underdamped dynamics when spatially homogeneous time-periodic c urrents are injected into the islands, and predict the existence of at tracting time-periodic spatially localised modes, for some ranges of j unction characteristic parameters. These elementary dynamical excitati ons are of two different types, associated to oscillatory and rotating motion of a few superconducting island phases, respectively, revealin g a dynamical mechanism of creation of vortex-antivortex pairs. These results are physical applications of recent advances in the theory of nonlinear dynamics of discrete macroscopic systems, Their experimental confirmation would probe the physical relevance of localisation in su perconducting devices. Copyright (C) 1998 Elsevier Science B.V.