Impurity scattering in highly anisotropic superconductors and interband sign reversal of the order parameter

TL;DR

This paper explores how impurity scattering affects the interband sign reversal of the order parameter in highly anisotropic multiband superconductors, extending theoretical models to include various anisotropies and impurity effects.

Contribution

It generalizes the Abrikosov-Gor'kov solution to arbitrary order parameter anisotropy, demonstrating that magnetic impurities can stabilize interband sign-reversal states.

Findings

Magnetic impurity scattering can stabilize interband sign reversal.

Theoretical extension to arbitrary anisotropy including d-wave pairing.

Possible relevance to experimental observations in YBa2Cu3O7.

Abstract

We discuss various mechanisms that can lead to interband sign reversal of the order parameter in a multiband superconductor. In particular, we generalize Abrikosov-Gor'kov solution of the problem of weakly coupled superconductor with magnetic and nonmagnetic impurities on the case of arbitary order parameter anisotropy, including extreme cases as $d-$pairing or interband sign reversal of the order parameter, and show that interband scattering by magnetic impurities can stabilize an interband sign-reversal state. We discuss a possibility of such state in YBa$_2$Cu$_3$O$_7$ in the context of various experiments: Josephson tunneling, neutron scattering, isotope effect measurements.