We report highly anomalous critical current vs. magnetic field dependencies of grain boundaries in YBa(2)Cu(3)O(7-x). Direct imaging with scanning SQUID microscopy provides evidence of magnetic flux generated by single grain boundaries. Conventional Josephson junction models cannot explain these effects if a superconducting order parameter with a pure s-wave symmetry is assumed. The results have significant implications for our understanding of the properties of grain boundaries in high-Tc superconductors and for their applications.
By: J. Mannhart, H. Hilgenkamp, B. Mayer, Ch. Gerber, J. Kirtley, K. A. Moler (Princeton Univ.) and M. Sigrist (ETH, Zurich, Switz.)
Published in: Proceedings of 10th Anniversary HTS Workshop on Physics, Materials and Applications ed. by B. Batlogg, C.W. Chu, W.K. Chu, D.U. Gubser and K.A. Müller. , Singapore, World Scientific, p.236-9 in 1996
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