Nonmagnetic impurity effects in MgB$_{2}$

TL;DR

This paper investigates how nonmagnetic impurities affect the superconducting properties of MgB₂, revealing a transition from two-gap to single-gap behavior and matching experimental specific heat data.

Contribution

It provides a detailed theoretical analysis of impurity effects in MgB₂ using a two-band model, aligning calculations with experimental observations.

Findings

Density of states transitions from two-gap to single-gap with increased impurity scattering

Excitation threshold varies non-monotonically with interband scattering

Calculated specific heat agrees well with irradiated sample experiments

Abstract

We study nonmagnetic impurity effects in MgB$_{2}$ using the quasiclassical equations of superconductivity for a weak-coupling two-band model. Parameters in the model are fixed so as to reproduce experiments on MgB$_{2}$ as closely as possible. The quasiparticle density of states and the specific heat are calculated for various values of the interband impurity scattering. The density of states changes gradually from a two-gap structure into the conventional single-gap structure as the interband scattering increases. It is found that the excitation threshold is not a monotonic function of the interband scattering. Calculated results for the specific heat are in good agreements with experiments on samples after irradiation.