Quantum critical phenomena in ladders of Josephson junctions in a magnetic field

摘要

A model of a ladder of Josephson junctions in a magnetic field is considered.The topological features of the zero-temperature phase diagram, as a functionof charging energy and small deviations from commensurability of the vortexlattice, are strongly dependent on the field. In addition tosuperconductor-insulator transitions, commensurate-incommensurate transitionsand depinning by quantum fluctuations of the vortex-lattice are also possible.the critical behavior of the superconductor-insulator transition at f = 1/2 isfound to depend on the ratio between interchain and intrachain Josephsoncouplings and is in the universality of the classical XY-Ising model.