Field-angle-resolved anisotropy in superconducting CeCoIn5using realistic Fermi surfaces

Abstract

We compute the field-angle-resolved specific heat and thermal conductivity using realistic model band structures for the heavy-fermion superconductor CeCoIn${}_{5}$ to identify the gap structure and location of nodes. We use a two-band tight-binding parametrization of the band dispersion as input for the self-consistent calculations in the quasiclassical formulation of the superconductivity. Systematic analysis shows that modest in-plane anisotropy in the density of states and Fermi velocity in tetragonal crystals significantly affects the fourfold oscillations in thermal quantities, when the magnetic field is rotated in the basal plane. The Fermi-surface anisotropy substantially shifts the location of the lines in the $H$-$T$ plane, where the oscillations change sign compared to quasicylindrical model calculations. In particular, at high fields, the anisotropy and sign reversal are found even for isotropic gaps. Our findings imply that a simultaneous analysis of the specific heat and thermal conductivity, with an emphasis on the low-energy sector, is needed to restrict potential pairing scenarios in multiband superconductors. We discuss the impact of our results on recent measurements of the Ce-115 family, namely, Ce$T$In${}_{5}$ with $T=$ Co, Rh, Ir.