Observation of Zero Crossing Shapiro Step on Current-Voltage Curve of Long YBa2Cu3O7-delta Bicrystal Josephson Junction Having Tilted Field Dependence

A YBa₂Cu₃O_7-δ bicrystal Josephson junction was fabricated by electron beam lithography and Ar ion beam etching. The width of the junction (W) was 12 μm and the Josephson penetration length (λ_J) was calculated to be 2.36 μm. As W/λ_J is 5.1, this bicrystal junction is a long Josephson junction. In critical current - magnetic field characteristics, periodicity is not observed, but the maximum value and the minimum value of the critical current are different at a finite magnetic field. In the I-V curve with irradiating the rf signal, the rounded Shapiro step was observed. By applying the magnetic field, the rounded 1st Shapiro step across the zero current axis was observed.