Evidence for tunneling and magnetic scattering at in situ YBCO/noble-metal interfaces

We report low-temperature conductance data for in situ YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO)/Ag, YBCO/Au, and YBCO/Pt planar c-axis interfaces. Analysis of the conductance data for these interfaces, which have resistivities as low as 1/spl times/10/sup -8/ /spl Omega//spl middot/cm/sup 2/, indicates that tunneling is the predominant transport mechanism. Zero-bias conductance peaks are present for all of the in situ interfaces. These peaks are analyzed in the framework of the Appelbaum model and are attributed to the presence of isolated magnetic spins at the interface. The presence and similarity of the peaks for each noble-metal overlayer supports the hypothesis that the magnetic spins are inherent to the YBCO surface.<
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