Phase transition and persistent current via excitonic transport in coupled Josephson necklaces

We study two necklaces of Josephson junctions, coupled capacitively with each other, in the presence of a magnetic field and gate charge induced by external sources. At zero temperature the system is mapped onto a two-dimensional classical Coulomb gas with spatially anisotropic interactions. controlled by the relative coupling capacitance. Such anisotropy. related with the action of excitonic particle-hole pairs, is found to suppress quantum fluctuations and to help establish superconductivity. similarly to the gate charge. The persistent current generated due to the magnetic field is observed to increase with the coupling capacitance. The increment in the side of the superconducting phase becomes more prominent as the transition point is approached, which manifests the significant role of the excitonic pairs in the system. (C) 2002 Elsevier Science B.V. All rights reserved.