Two-gap superconductivity in MgB$_{2}$: clean or dirty?

TL;DR

This paper discusses the two-gap superconductivity in MgB₂, addressing discrepancies between theoretical predictions and experimental observations by considering band disparity in electronic structure.

Contribution

It introduces the importance of band disparity in understanding the lack of correlation between critical temperature and residual resistivity in MgB₂.

Findings

Two-gap model aligns with experimental facts

Band disparity explains the absence of T_c and resistivity correlation

Impurity scattering effects are mitigated by electronic structure considerations

Abstract

A large number of experimental facts and theoretical arguments favor a two-gap model for superconductivity in MgB$_{2}$. However, this model predicts strong suppression of the critical temperature by interband impurity scattering and, presumably, a strong correlation between the critical temperature and the residual resistivity. No such correlation has been observed. We argue that this fact can be understood if the band disparity of the electronic structure is taken into account, not only in the superconducting state, but also in normal transport.