Critical currents of composite superconductors: Model calculations

Journal Article · Sat Feb 01 00:00:00 EST 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.45.2417· OSTI ID:7272823

Lee, K H; Stroud, D ^[1]

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1. Department of Physics, The Ohio State University, 174 West 18th Avenue, Columbus, Ohio 43210 (United States)

We calculate the {ital I}-{ital V} characteristics of composite superconductors modeled as random three-dimensional arrays of resistively shunted Josephson junctions at zero temperature, in zero and finite applied magnetic fields. Two types of disorder are considered: site dilution of a simple cubic lattice to a concentration {ital p} and a random displacement of grains in an ordered lattice. In the site-diluted lattice, we find that there exists a critical current density {ital J}{sub {ital c}}({ital p}), below which the voltage becomes very small, and which varies as a power law in ({ital p}{minus}{ital p}{sub {ital c}}), {ital J}{sub {ital c}}({ital p}){proportional to}({ital p}{minus}{ital p}{sub {ital c}}){sup {ital v}} with {ital v}{approx}1.7, in agreement with previous static estimates and in qualitative agreement with experimental studies on Ag/YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} composites. Near the percolation threshold {ital p}{sub {ital c}}, we find a scaling relation between the current density {ital J} and the electric field {ital E}, analogous to that proposed by Fisher {ital et} {ital al}. near the vortex-glass transition in superconductors with microscopic disorder. In the presence of an applied magnetic field, we find numerically that the critical current initially decreases with field, then reaches a plateau. We present qualitative arguments to estimate both the crossover field {ital H}{sub {ital X}} at which the plateau is approached, and the value of the critical current density on the plateau. Possible connections between these results and the large plateau fields and critical currents observed by Sato {ital et} {ital al}. (IEEE Trans. Magn. MAG-27, 1231 (1991)) are discussed.

• DOE Contract Number: FG02-90ER45427
• OSTI ID: 7272823
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 45:5; ISSN 0163-1829
• Country of Publication: United States
• Language: English

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75 CONDENSED MATTER PHYSICS
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