Anisotropic distributions of electrical currents in high-Tc grain-boundary junctions
M. Yu. Kupriyanov, M. M. Khapaev, Y. Y. Divin*+, V. N. Gubankov+
Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics, 119991 Moscow, Russia
*Peter Gruenberg Institute, Forschungszentrum Juelich, 52425 Juelich, Germany
+Kotel'nikov Institute of Radio Engineering and Electronics of the RAS, 125009 Moscow, Russia
Abstract
We developed a self-consistent method for calculations of spatial current distributions in
high-Tc grain-boundary junctions. It is found that crystallographic anisotropy of high-
Tc superconducting electrodes results in the effects, which previously were not
taken into account for interpretations of experimental data. Among them is a significant
redistribution of electrical currents in superconducting electrodes in the vicinity of a grain
boundary. In particular in the case of [100]-tilt bicrystal junctions, this current redistribution
results in a substantial focusing to the top or bottom part of a thickness of the grain
boundary, depending on "roof"- or "valley"-type of the grain boundary. This redistribution is
accompanied by generation of vortex currents around the grain boundary, which leads to
selfbiasing of grain-boundary junctions by magnetic field nucleated by these vortex
currents. It is shown that twinning or variation of geometrical shape of the high-Tc
electrode may also result in intensive redistribution of electrical currents and nucleation of
local magnetic fields inside a high-Tc superconducting electrodes.