Abstract:We demonstrate a zero-crossing Shapiro step generated in a magnetically-coupled Josephson gate, where a long Josephson junction and a control line are placed in-line. The operation is based on the imbalanced evolution of the junction phases owing to the different amplitudes of the positive and negative critical current. A test circuit was fabricated using a Nb/AlO x /Nb junction technology. When we applied a rf signal of 15.2 GHz, we observed a Shapiro step that crossed the zero-current axis at the voltage position of the 1st order. The experimental results were quantitatively reproduced by simulation.
A YBa 2 Cu 3 O 7-δ bicrystal Joseph hson junction was (a) fabricated by electron beam lithography an nd Ar ion beam etching. The width of the junction (W) was 12 μm and the Josephson penetration length (λ J ) was calculate ed to be 2.36 μm. As W/λ J is 5.1, this bicrystal junction is a long Jo osephson junction. In critical current -magnetic field characterist tics, periodicity is not observed, but the maximum value and the m minimum value of the critical current are different at a finite mag gnetic field. In the I-V curve with irradiating the rf signal, the roun nded Shapiro step was observed. By applying the magnetic field, , the rounded 1st Shapiro step across the zero current axis was ob bserved.(b)
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