Two-dimensional magnetic field dependence of current-voltage characteristics of rectangular, hexagonal and triangle shape superconducting junctions and DC-SQUIDs

Modulation characteristics of Josephson current through rectangular, hexagonal and triangle shape superconducting junctions and dc-SQUIDs by two-dimensional scanning of external magnetic field have been studied. Two pairs of Helmholtz coils were controlled by two current sources with GPIB (General Purpose Interface Bus) system to obtain the magnetic field dependence automatically. In the case of rectangular shape junction, the dependence of Josephson current on Hx-Hy plane has become the product of the two Fraunhofer patterns in the direction Hx, Hy parallel to each edge of this rectangular shape. The periods of these modulations were inversely proportional of each length of the rectangular shape perpendicular to the magnetic field. In the case of hexagonal shape junction, we have found hexagonal symmetry in the dependence of Josephson current on the Hx-Hy plane. Six ridges of the modulation surface were clearly observed in the directions of six edges of the hexagonal shape (0, 60, 120, 180, 240 300 degrees). In triangle shape junctions, six ridges of the modulation surface were also clearly observed in the directions of three edges of the triangle shape. In the case of dc-SQUIDs, the modulation pattern was the product of the sensitive modulation of the period of the magnetic flux quantization of the hole of the vertical dc-SQUID and the insensitive modulation pattern of each square junction itself.