Probing the order parameter using cross-whisker junction with adjustable Josephson characteristics

Cross-whisker intrinsic Josephson junction has been developed as a probe of symmetry of the superconducting order parameter. Two B2212 single crystal whiskers were connected on a MgO substrate at their c-plane with various crossing angles. Angular dependence of the critical current densities showed d-wave-like 4-fold symmetry. However, the angular dependence was much stronger than that of the conventional dx2-y2-wave. The critical current density of the cross-whisker junction with cross-angle α=45 deg. was not completely zero. Shapiro steps and Fraunhofer pattern were clearly observed in 45 deg. twisted cross-whisker junctions. It is suggested that the superconducting gap exists even at nodal direction