Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 9: SC: Poster Session
TT 9.11: Poster
Montag, 22. März 2010, 14:00–18:00, Poster A
Suppression of the critical current at grain boundaries of high-temperature superconductors — •Siegfried Graser1, Thilo Kopp1, Jochen Mannhart1, Raphael Gutser1, Peter Hirschfeld2, and Brian M. Andersen3 — 1Zentrum für Elektronische Korrelationen und Magnetismus, Institut für Physik, Universität Augsburg — 2Department of Physics, University of Florida, Gainesville, FL (USA) — 3Niels Bohr Institute, University of Copenhagen, Copenhagen (Denmark)
The interface properties of high-temperature cuprate superconductors (HTS) have been of interest for many years, and play essential roles in Josephson junctions, superconducting cables, and microwave electronics. In particular, the maximum critical current achievable in HTS wires and tapes is well known to usually be limited by the presence of grain boundaries, regions of mismatch between crystallites with misoriented crystalline axes. In studies of single, artificially fabricated grain boundaries the striking observation has been made that in a variety of HTS materials, the critical current Jc of a grain boundary junction depends exponentially on the misorientation angle. Until now microscopic understanding of this apparently universal behavior has been lacking. We present here the results of microscopic evaluations in which we construct fully 3D YBCO grain boundaries by molecular dynamics. With these structures the critical current in a d-wave superconductor is shown to follow an exponential reduction with grain boundary angle. We identify the build up of charge inhomogeneities to be the dominant mechanism for the suppression of the supercurrent.