Quasi-particle lifetime broadening in normal—superconductor junctions with UPt 3

Abstract

For the Andreev-reflection process of quasi-particles at a normal-metal—superconductor interface the influence of lifetime broadening of the quasi-particles on the current-voltage characteristics of NS point contacts is analyzed along the lines of the Blonder—Tinkham—Klapwijk model. The anomalous Andreev-reflection spectra obtained for the heavy-fermion compound UPt 3 cannot be explained by lifetime broadening alone. Instead, an anisotropic superconducting order parameter has to be assumed which, if also lifetime broadening is included, leads to a fairly good agreement with the data.