Correlation betweend-wave pairing behavior and magnetic-field-dependent zero-bias conductance peak

Abstract

We consistently observe a magnetic-field-dependent conductance peak at zero-bias voltage in a wide range of superconductor/noble-metal junctions fabricated from oxide superconductors (${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ and ${\mathrm{Tl}}_2{\mathrm{Ba}}_2{\mathrm{CaCu}}_2\mathrm{O}$) that have been reported to exhibit $d$-wave pairing behavior; however, no measurable peak appears in similar junctions made from an $s$-wave oxide superconductor $\left({\mathrm{Nd}}_{1.85}{\mathrm{Ce}}_{0.15}{\mathrm{CuO}}_4\right).\mathrm{}$ Explanations of this correlation are considered in terms of the Appelbaum-Anderson model for magnetic interface scattering and the midgap-state model for $d$-wave interface states.