EXPLANATION OF THE ZERO-BIAS ANOMALY IN THE TUNNELING CHARACTERISTICSOF SINGLE-CRYSTAL BI2SR2CACU2O8 WITH INTRINSIC JOSEPHSON TUNNELING

We present measurements of dV/dI vs. I for Ag-single crystal Bi2Sr2CaC u2O8-Ag NSN contacts. It was found that when the contact resistance wa s comparable to the sample resistance, zero bias anomalies, as previou sly reported, were observed. We explain this observation by assuming t hat the sample contains intrinsic Josephson junctions between the CuO planes which become normal at higher current densities.