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 Ic 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 a 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 behaviour 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 those 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. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
CITATION STYLE
Sodano, P., Trombettoni, A., Silvestrini, P., Russo, R., & Ruggiero, B. (2006). Inhomogeneous superconductivity in comb-shaped Josephson junction networks. New Journal of Physics, 8. https://doi.org/10.1088/1367-2630/8/12/327
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