Anisotropic distributions of electrical currents in high-${T_{c}}$ grain-boundary junctions

We developed a self-consistent method for calculations of spatial current distributions in high-$T_{c}$ grain-boundary junctions. It is found that crystallographic anisotropy of high- $T_{c}$ 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-$T_{c}$ electrode may also result in intensive redistribution of electrical currents and nucleation of local magnetic fields inside a high-$T_{c}$ superconducting electrodes.