Differential conductance of point contacts between an iron-based superconductor and a normal metal

Abstract

We present a theoretical description of the differential conductance of point contacts between a normal metal and a multiband superconductor with extended ${s}^{\ifmmode\pm\else\textpm\fi{}}$ pairing symmetry. We demonstrate that the interband impurity scattering broadens the coherent peak near the superconducting gap and significantly reduces its height even at relatively low scattering rates. This broadening is consistent with a number of recent experiments performed for both tunnel junctions and larger diffusive contacts. Our theory helps to better evaluate the energy gap of iron-based superconductors from point-contact Andreev spectroscopy measurements.