Reduction in Shapiro Step Height in Double-Barrier Josephson Junction Arrays

The relationships between the height of the constant voltage step and the difference in the critical current I c or normal resistance R n of the upper and lower junctions were numerically calculated. The dependence of the step height on the distribution of the microwave power in a Josephson junction array was also numerically calculated. As a result, it was shown that the difference in R n significantly reduced the height of the steps, while the uniformity of R n was actually excellent in our previous experiments. On the other hand, neither the difference in I c nor the distribution of the microwave power due to attenuation at junctions significantly reduced the step height. The numerical analysis implied that the standing waves in the array due to an impedance mismatch will also significantly reduce the step height.