Quasiparticle injection into YBCO four terminal Josephson devices

The transport properties of three terminal Josephson devices based on quasiparticle injection into YBa2Cu3O7-delta step-edge junctions have been studied. A surface layer with small electronic mean free path is used in examining the effects of surface roughness. Results indicate the presence of isotropic superconducting state in the layer. The surface density is gapless and shows an number of finite bias peaks while the midgap peak appears only at small roughness parameter.