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Tunnelling in and The Microstructure of Granular Superconductors

Published online by Cambridge University Press:  10 February 2011

D. S. McLachlan  and
R. Rosenbaum
D. S. McLachlan
Affiliation:
Physics Department, University of the Witwatersrand, Johannesburg 2050.
R. Rosenbaum
Affiliation:
Physics Department, Tel Aviv University, Tel Aviv 69978.
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Abstract

The microstructure of granular superconductors are discussed and the difference between granular and random composites is noted. The model where a granular (and a random) superconductor, close to the percolation threshold, is considered to be made up of large granular clusters, linked by tunnelling junctions or weak links, is introduced. This model is illustrated using recent experimental measurements on nanostructured granular Aℓ–Ge. The measurements clearly show that the coupling junctions between clusters can,depending on the volume fraction of superconductor, be of either a Josephson or quasi–particle nature, or a combination of both. The differences between a granular and adirty superconductor and the upper critical field of granular superconductors is then discussed and it is shown that the diameter of the grains can be estimated from the upper critical field. Random Aℓ–Ge, which has a rather different microstructure, is also discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 411: Symposium T – Electricaly-Based Microstructural Characterization , 1995 , 321
Copyright
Copyright © Materials Research Society 1996

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References

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