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 d(x2-y2)-wave. The critical current density of the cross-whisker junction with cross-angle alpha = 45degrees was not completely zero. Shapiro steps and Fraunhofer pattern were clearly observed in 45degrees twisted cross-whisker junctions. It is suggested that the superconducting gap exists even at nodal direction. (C) 2004 Elsevier B.V. All rights reserved.