Microwave conductivity of d-wave superconductors with extended impurities

TL;DR

This paper studies how extended impurities affect microwave conductivity in d-wave superconductors, improving theoretical models to better match experimental data for YBCO and BSCCO, and linking impurity scattering to material disorder.

Contribution

It generalizes a previous quasiparticle scattering model to include extended impurities, providing better explanations for experimental microwave spectra in high-Tc superconductors.

Findings

Extended scatterers improve fit to YBCO microwave data.

Large concentration of weak-to-intermediate scatterers needed for BSCCO.

Results align with ARPES and STM studies indicating forward scattering.

Abstract

We investigate the influence of extended scatterers on the finite temperature and finite frequency microwave conductivity of d-wave superconductors. For this purpose we generalize a previous treatment by Durst and Lee, which is based on a nodal approximation of the quasiparticle excitations and scattering processes, and apply it to the analysis of experimental spectra of YBCO-123 and BSCCO-2212. For YBCO, we find that accounting for a slight spatial extension of the strong scattering in-plane defects improves the fit of the low temperature microwave conductivity to experiment. With respect to BSCCO we conclude that it is necessary to include a large concentration of weak-to-intermediate strength extended scatterers, which we attribute to the out-of plane disorder introduced by doping. These findings for BSCCO are consistent with similar analyses of the normal state ARPES spectra and of STM spectra in the superconducting state, where an enhanced forward scattering has been inferred as well.