Correlation between specular Andreev reflection and zero-energy states in normal-metal/d-wave-superconductor junctions -: art. no. 064522

We report the effects of interfacial roughness on a zero-bias conductance peak (ZBCP) in normal-metal/d-wave-superconductor junctions. The roughness spoils to specularity of the junction interface, and causes a diffuse Andreev reflection of a quasiparticle. The ZBCP decreases linearly with a decreasing rate of the specular Andreev reflection at the interface. A sensitivity of the ZBCP to the roughness strongly depends on a transparency of the junctions. In low transparent junctions, the ZBCP disappears even in the regime of weak roughness. We also find a splitting of the ZBCP owing to the inter-facial roughness in low transparent junctions.