RESONANT-TUNNELING TRANSPORT ACROSS YBA2CU3O7-SRRUO3 INTERFACES

We have investigated superconductor-normal metal-superconductor juncti ons with metallic perovskite SrRuO3 barriers. Ramp-type junctions with ion-beam-etched and wet-chemical-etched YBa2CU3O7 (YBCO) ramps have b een compared with planar junctions where the interfaces were fabricate d completely in situ. Regardless of the fabrication method, the juncti on properties were determined not by the metallic SrRuO3 barrier, but by an insulating layer at the interface. The shape of the I-V curves, and the temperature dependence of the normal resistance of junctions, could be well explained by quasiparticle resonant tunneling via two lo calized states in the interface layer. Furthermore, a model for the Co oper pair transport will be discussed that assumes resonant tunneling via one localized state as transport mechanism. (C) 1995 American Inst itute of Physics.