Percolation and Electrical Conduction in Superconducting Composites.
Abstract
We report the experimental properties of a number of random superconducting-normal metal composites. Theoretical interpretation is also presented, with emphasis on the effects of geometrical randomness. The electrical properties of in situ multifilamentary Cu-V3Ga wires are discussed, with emphasis on critical current and field properties which are relevant to applications. We found that these wires had upper critical fields as high as 22.4T at 4.2K with a transition temperature of 15.5K. Their overall critical current density compared favorably with commercial wires. The results of electrical measurements on in situ Cu alloy-Nb composites are reported which elucidate the roles of percolation and the proximity effect in these materials. Our data show that the proximity effect is very important in clean, low superconducting concentration samples, with geometrical percolation being more important as the matrix becomes dirtier. In addition, we discuss models for the superconducting to normal transition in these materials which include the effects of randomness and thermal fluctuations. A two-dimensional thin film system based on Cu-Pb is discussed and shown to be qualitatively similar to the three-dimensional in situ composites.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1980
- Accession Number
- ADA088196
Entities
People
- Christopher J. Lobb
Organizations
- Harvard University