Hysteresis in Josephson current by magnetic flux quantum

The modulation of the Josephson current is usually performed by applying the external magnetic field parallel to the Josephson junction. The modulation characteristic of the Josephson current have been measured by applying an external magnetic field H_z in the direction perpendicular to the Josephson junction. A hysteresis in the Josephson current was found when sufficiently strong magnetic field H_z is applied in the direction perpendicular to the Josephson junction for the first time. If the strong magnetic field H_z is applied, the magnetic flux quantum is trapped in the superconducting film. The hysteresis in the Josephson current is thought to have been caused by vortex. This time, the Josephson current was modulated by applying the external magnetic field H_x parallel to the Josephson junction and applying the external magnetic field H_z perpendicular to the Josephson junction two-dimensionally. So the hysteresis in the Josephson current for the external magnetic field H_z was observed.