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

TL;DR

This paper provides a theoretical model for the differential conductance in point contacts between a normal metal and a multi-band iron-based superconductor, explaining experimental observations and aiding in gap estimation.

Contribution

It introduces a theoretical framework accounting for interband impurity scattering effects on conductance spectra in iron-based superconductors.

Findings

Interband impurity scattering broadens the superconducting gap peak.

Impurity scattering reduces the peak height in conductance spectra.

The theory aligns with recent experimental data.

Abstract

We present a theoretical description of the differential conductance of point contacts between a normal metal and a multi-band superconductor with extended s\pm 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.