2 research outputs found
Superconductor-insulator duality for the array of Josephson wires
We propose novel model system for the studies of superconductor-insulator
transitions, which is a regular lattice, whose each link consists of
Josephson-junction chain of junctions in sequence. The theory of such
an array is developed for the case of semiclassical junctions with the
Josephson energy large compared to the junctions's Coulomb energy .
Exact duality transformation is derived, which transforms the Hamiltonian of
the proposed model into a standard Hamiltonian of JJ array. The nature of the
ground state is controlled (in the absence of random offset charges) by the
parameter , with superconductive state
corresponding to small . The values of are calculated for
magnetic frustrations and . Temperature of superconductive
transition and is estimated for the same values of . In
presence of strong random offset charges, the T=0 phase diagram is controlled
by the parameter ; we estimated critical value
.Comment: 5 pages, 2 figure
Inhomogeneous Superconductivity in Comb-Shaped Josephson Junction Networks
We show that some of the Josephson couplings of junctions arranged to form an
inhomogeneous network undergo a non-perturbative renormalization provided that
the network's connectivity is pertinently chosen. As a result, the zero-voltage
Josephson critical currents turn out to be enhanced along directions
selected by the network's topology. This renormalization effect is possible
only on graphs whose adjacency matrix admits an hidden spectrum (i.e. a set of
localized states disappearing in the thermodynamic limit). We provide a
theoretical and experimental study of this effect by comparing the
superconducting behavior of a comb-shaped Josephson junction network and a
linear chain made with the same junctions: we show that the Josephson critical
currents of the junctions located on the comb's backbone are bigger than the
ones of the junctions located on the chain. Our theoretical analysis, based on
a discrete version of the Bogoliubov-de Gennes equation, leads to results which
are in good quantitative agreement with experimental results.Comment: 4 pages, 2 figures, revte