Influence of the position of the Josephson junction in the base Nb layer on modulation characteristics of the Josephson current

Abstract

We measured the two-dimensional magnetic field dependence of a Josephson current through an Nb/Al-AlOx/Nb Josephson tunnel junction by applying external magnetic fields (Hx, Hy) parallel to the junction plane from two directions. We obtained much information about current distribution within the Josephson junction from a two-dimensional scan of the external magnetic fields (Hx, Hy). We also measured the perpendicular magnetic field Hz dependence of a Josephson current. When the perpendicular magnetic field Hz was applied to the Josephson junction, the Josephson current was modulated by the parallel component of the applied magnetic field Hz produced by the Meissner effect of the base Nb layer. In this study, some Josephson junctions were fabricated on the base Nb layer in our sample, and we investigated how the position of the Josephson junction on the base Nb layer influenced the modulation characteristics of the Josephson current when the perpendicular magnetic field Hz was applied to the junction. The junction at the center of the base Nb layer was not easily affected by the perpendicular magnetic field Hz because of the Meissner effect of the base Nb layer, whereas the junction on the edge of the base Nb layer was susceptible to the perpendicular magnetic field Hz.