Percolating granular superconductors

Hans-Karl Janssen; Olaf Stenull

doi:10.1103/PhysRevE.67.046115

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Percolating granular superconductors

Hans-Karl Janssen, Olaf Stenull

DOI 10.1103/PhysRevE.67.046115 · Physical Review E

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Abstract

We investigate diamagnetic fluctuations in percolating granular superconductors. Granular superconductors are known to have a rich phase diagram including normal, superconducting, and spin-glass phases. Focusing on the normal-superconducting and the normal-spin-glass transition at low temperatures, we study the diamagnetic susceptibility χ(1) and the mean square fluctuations of the total magnetic moment χ(2) of large clusters. Our work is based on a random Josephson network model that we analyze with the powerful methods of renormalized field theory. We investigate the structural properties of the Feynman diagrams contributing to the renormalization of χ(1) and χ(2). This allows us to determine the critical behavior of χ(1) and χ(2) to arbitrary order in perturbation theory.