Anomalous structures in point contact Andreev reflection spectrum

Abstract

We report the systematic study of the anomalous structures viz. dips and large zero bias enhancement in point contact Andreev reflection spectrum obtained between a normal metal and a superconductor. These are not explained in Blonder–Tinkham–Klapwizk formalism, which is conventionally used for analyzing normal metal–superconductor ballistic point contacts. We demonstrate that the anomalous structures are due to the contribution from the critical current of the point contact to the contact resistance when the contact is not in the pure ballistic regime.