Minimal model of point contact Andreev reflection spectroscopy of multiband superconductors

TL;DR

This paper introduces a minimal, analytically solvable model for point contact Andreev reflection spectroscopy in multiband superconductors, extending the BTK theory to better interpret experimental data.

Contribution

It generalizes the BTK model to multiband superconductors using quantum waveguides, enabling analytic calculation of reflection coefficients for experimental data fitting.

Findings

Differential conductance curves show features matching experimental data.

Model applicable to iron-based pnictides and MgB2.

Provides a tool for analyzing multiband superconductor interfaces.

Abstract

We formulate a minimal model of point contact Andreev reflection spectroscopy of a normal- metal/multiband superconductor interface. The theory generalizes the Blonder-Tinkham-Klapwijk (BTK) formulation to a multiband superconductor and it is based on the quantum waveguides theory. The proposed approach allows an analytic evaluation of the Andreev and normal reflection coefficients and thus is suitable for a data fitting of point contact experiments. The obtained differential conductance curves present distinctive features similar to the ones measured in the experiments on multiband systems, like the iron-based pnictides and the MgB2.