Gapless Fermi Surfaces in Superconducting CeCoIn5?

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.