Observations of the ac Josephson effect in Y-Ba-Cu-O superconductors at 77 K

The observations of the ac Josephson effect in Y-Ba-Cu-O superconducting weak link were reported. The Y-Ba-Cu-O sample had a Tc = 90 K. The I-V characteristics of the weak link junction were measured at 77 K. The junction had a Ic = O.43 mA and the normal resistance Rn 0.38 ohm. 10.15 GHz microwave was applied to the junction and the rf-induced steps up to n 10 were observed. The dependence of the step height on the rf level was in agreement with ordinary Josephson tunneling behavior. (author)