Quasi-particle and pair current steps of Josephson junctions with radiation noise in a DC magnetic field

The current-voltage characteristics of a Josephson junction approximated by a long interferometer with many point junctions are simulated under the influence of a local oscillator at about half the gap frequency for different oscillator resistances. Without a DC magnetic field, pair current steps with hysteresis and quasi-particle steps appear in the same I-V characteristic. With appropriate magnetic fields, Shapiro steps can be reduced. However, even at the first and second zeros of the Josephson current, Shapiro steps of finite size are simulated. Modifications of current steps are described as a function of local oscillator noise. The simulated results are in qualitative agreement with measurements reported in the literature