| Studies of the current carrying capability of grain boundaries in the High Temperature Superconductors have not only helped researchers to determine the pairing symmetry of the superconducting electrons, but also helped to improve the overall critical current density of the material. Previous work had found that transboundary current density depended only on the misorientation angle of the grain boundary and the current density decreased exponentially with increasing misorientation. However, the issue was complicated by the fact that electron pairings of High Temperature Superconductors had d-wave symmetry. Since the grain boundaries have tendency to meander and facet locally, it meant the matching of the lobes and nodes in the wavefunctions across the boundary interface locally would introduce an additional phase variation in the critical current density across the boundary. This additional phase variation was not previously considered because the HTS was at first thought to have s-wave pairing symmetry. Here, we attempt to quantify such effect both with a model and experiment by using non-faceted bicrystal grain boundaries with known inclinations. Experimentally, the Scanning SQUID microscope allows us to probe the local current density of a grain boundary without obscuration by the flux interacting with each other. In this case, the current density across the grain boundary can be determined by knowing the flux penetration length along the grain boundary. In our study, the variation in inclination is shown to be a second order effect. The misorientation angle still determines the coupling strength of the boundary. |
