Competing effects of surface phonon softening and quantum size effects on the superconducting properties of nanostructured Pb

Abstract

The superconducting transition temperature (TC) in nanostructured Pb remains nearly constant as the particle size is reduced from 65 to 7nm, below which size the superconductivity is lost rather abruptly. In contrast, there is a large enhancement in the upper critical field (HC2) in the same size regime. We explore the origin of the unusual robustness of the TC over such a large particle size range in nanostructured Pb, by measuring the temperature dependence of the superconducting energy gap in planar tunnel junctions of Al/Al2O3/nano-Pb. We show that below 22nm, the electron phonon coupling strength increases monotonically with decreasing particle size, and almost exactly compensates for the quantum size effect, which is expected to suppress TC.

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References in corpus (8)

• Eigenfunction fractality and pseudogap state near superconductor-insulator transition
• Size dependence of the Tc and the superconducting energy gap in nanocrystalline thin films of Nb
• Upper critical field in nanostructured Nb: Competing effects of the reduction in density of states and the mean free path
• Magnetization of small lead particles
• Universal transport in 2D granular superconductors
• Evidence of gap anisotropy in superconducting YNi2B2C using directional point contact spectroscopy
• Size induced metal insulator transition in nanostructured Niobium thin films: Intragranular and intergranular contributions
• Critical currents and vortex-unbinding transitions in quench-condensed ultrathin films of Bismuth and Tin

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