Fate of global superconductivity in arrays of long SNS junctions

Abstract

Normal-metal films overlaid with arrays of superconducting islands undergo Berezinskii-Kosterlitz-Thouless (BKT) superconducting transitions at a temperature $T_{BKT}$. We present measurements of T${}_{BKT}$ for arrays of mesoscopic Nb islands patterned on Au films for a range of island spacings $d$. We show that $T_{BKT}\sim 1/d^2$, and explain this dependence in terms of the quasiclassical prediction that the Thouless energy, rather than the superconducting gap, governs the inter-island coupling. We also find two deviations from the quasiclassical theory: (i) $T_{BKT}$ is sensitive to island height, because the islands are mesoscopic; and (ii) for widely spaced islands the transition appears to lead, not to a superconducting state, but to a finite-resistance "metallic" one.

12 pages, 4 figures

References in corpus (4)

• Extremely strong coupling superconductivity in artificial two-dimensional Kondo lattices
• Theory of quantum metal to superconductor transitions in highly conducting systems
• Proximity DC squids in the long junction limit
• Josephson current in nanofabricated V/Cu/V mesoscopic junctions

Cited by in corpus (5)

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• Local imaging of diamagnetism in proximity coupled niobium nano-island arrays on gold thin films
• Current Conservation in the Self-Consistent Josephson Junction
• DC-operated Josephson junction arrays as a cryogenic on-chip microwave measurement platform