The superconducting proximity effect in epitaxial Al/Pb nanocomposites

Superconductor Science and Technology  2014 ,Volume 27, Number 1.

H Wang1, T Picot2, K Houben2, T Moorkens2, J Grigg3, C Van Haesendonck2, E Biermans4, S Bals4, S A Brown3, A Vantomme1, K Temst1 and M J Van Bael2

 

1 Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium  and
2 Laboratorium voor Vaste-Stoffysica en Magnetisme, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium  and
3 The MacDiarmid Institute for Advanced Materials and Nanotechnology, Department of Physics and Astronomy, University of Canterbury, 8140, Christchurch, New Zealand and
4 Elektronenmicroscopie voor Materiaalonderzoek, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.

 

 

 

Abstract

 

We have investigated the superconducting properties of Pb nanoparticles with a diameter ranging from 8 to 20 nm, synthesized by Pb+ ion implantation in a crystalline Al matrix. A detailed structural characterization of the nanocomposites reveals the highly epitaxial relation between the Al crystalline matrix and the Pb nanoparticles. The Al/Pb nanocomposites display a single superconducting transition, with the critical temperature Tc increasing with the Pb content. The dependence of Tc on the Pb/Al volume ratio was compared with theoretical models of the superconducting proximity effect based on the bulk properties of Al and Pb. A very good correspondence with the strong-coupling proximity effect model was found, with an electron–phonon coupling constant in the Pb nanoparticles slightly reduced compared to bulk Pb. Our result differs from other studies on Pb nanoparticle based proximity systems where weak-coupling models were found to better describe the Tc dependence. We infer that the high interface quality resulting from the ion implantation synthesis method is a determining factor for the superconducting properties. Critical field and critical current measurements support the high quality of the nanocomposite superconducting films.

© 2014 IOP Publishing Ltd

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