A qualitative explanation of tunneling characteristics of high-Tc junctions in terms of the McMillan proximity model

In this paper the influence of proximity effects on the transport properties of high-T_c superconductors is considered. On the basis of the experimental results on tunneling spectroscopy reported in the current literature, we discuss some of the main features ofdI/dV vs.V characteristics. More particularly, attention is focused on the depression of gap structure, the presence of conductance peaks due to the counterelectrode gap, and “zero-bias anomalies.” A possible explanation of those features in terms of the McMillan proximity model is given along with some examples of application of the model to experimental data.