Gapless Fermi Surfaces in Superconducting CeCoIn5?

TL;DR

This paper models the effects of impurities on multi-band superconductivity in CeCoIn5, showing how defects influence the gaps and restore normal metallic behavior, aligning with experimental observations.

Contribution

It introduces a two-band model to explain impurity effects on superconducting gaps and thermal properties in CeCoIn5, highlighting the role of induced gaps on uncondensed Fermi surfaces.

Findings

Impurities reduce the induced gap on the second Fermi surface.

Restoration of the Wiedemann-Franz law occurs with increased impurity scattering.

Model results agree with experimental data on specific heat and thermal conductivity.

Abstract

According to [M.A. Tanatar et al., Phys. Rev. Lett. 95, 067002 (2005)], in a multi-band d-wave superconductor CeCoIn5 electrons remain partially uncondensed. Interactions must induce superconducting order on all Fermi surfaces. We calculate specific heat and thermal conductivity in a two band model in presence of defects. Superconductivity originates on one Fermi surface, inducing a smaller gap on the other. Impurities diminish the induced gap and increase the density of states, restoring rapidly the Wiedemann-Franz law for this Fermi surface. Our calculations are in agreement with experiment.