All-Ceramics Josephson Junctions Operative up to 90 K

Abstract

Ba-Y-Cu-O/Ba-Y-Cu-O Josephson junctions are made by creasing fissures in the bulk Ba-Y-Cu-O ceramic superconductors. The critical current of the junction fissured at room temperature decreases exponentially with the increase in the operating temperature, similar to that of an S/N/S junction. However, with the junction fissured at cryogenic temperature, critical current persists all the way up to about 90 K (T _c of Ba-Y-Cu-O compound). The a.c. Josephson effectis observed for these junctions in all temperature range up till 90 K. The onset of the formation of the macroscopic quantum state just below 90 K is implied.