Incoherent Non-Fermi Liquid Scattering in a Kondo Lattice

The effect of Kondo lattice dilution was investigated in the heavy-fermion superconductor CeCoIn$_5$ to study the evolution of unconventional superconductivity and non-Fermi liquid properties. A systematic substitution of both non-magnetic (full or empty $f$-shell) and large, stable $f$-moment rare earth impurities into high-quality single-crystal specimens of Ce$_{1-x}$R$_x$CoIn$_5$ (where R=Y, Pr, Gd, Er and Lu) has revealed two contrasting features. First, both superconducting electron pair-breaking and the suppression of Kondo coherence proceed in a manner which is insensitive to the magnetic state of the dopant atom, suggesting spin-independent disorder is the dominant perturbation in both phenomena. In contrast, the evolution of the non-Fermi liquid properties with substitution shows a striking sensitivity to the dopant atom's f-moment configuration.