High temperature superconducting Josephson junctions in a stacked bicrystal geometry

Bicrystal grain boundary Josephson junctions were fabricated in a stack of two layers of YBa2Cu3Oχ separated by epitaxial SrTiO3. Weak link behavior was observed in the bridges formed in both layers that had similar shunted-junction characteristics but significantly different critical currents. Characteristic voltages up to 1.9 mV were measured at 4.5 K. The resonant structure was seen in the current–voltage characteristics of the upper-layer junctions, and interactions between junctions in the two layers were evident