Angular Position of Nodes in the Superconducting Gap of Quasi-2D Heavy-Fermion SuperconductorCeCoIn5

Abstract

The thermal conductivity of the heavy-fermion superconductor ${\mathrm{CeCoIn}}_{5}$ has been studied in a magnetic field rotating within the 2D planes. A clear fourfold symmetry of the thermal conductivity which is characteristic of a superconducting gap with nodes along the ( $\ifmmode\pm\else\textpm\fi{}\ensuremath{\pi},\ifmmode\pm\else\textpm\fi{}\ensuremath{\pi}$) directions is resolved. The thermal conductivity measurement also reveals a first-order transition at ${H}_{c2}$, indicating a Pauli limited superconducting state. These results indicate that the symmetry most likely belongs to ${d}_{{x}^{2}{\ensuremath{-}y}^{2}}$, implying that the anisotropic antiferromagnetic fluctuation is relevant to the superconductivity.