Modulation of Josephson current of Nb junctions by two-dimensional scan of external magnetic field

Josephson current of superconducting junctions can be modulated by an external field. This modulation of the Josephson current I/sub c/ is usually observed by one-dimensional scan of the applied magnetic field. In this paper, using two pairs of the Helmholz coils, the external magnetic field H is scanned in two dimensions and the two-dimensional surfaces of the I/sub c/-H dependence are first measured. Modulations of Fiske steps of the current-voltage characteristics are also studied.