Optical signatures of momentum-dependent hybridization of the local moments and conduction electrons in Kondo lattices

The effect of magnetic moments on superconductivity has long been acontroversial subject in condensed matter physics. While Matthias andcollaborators experimentally demonstrated the destruction of superconductivityin La by the addition of magnetic moments (Gd), it has since been suggestedthat magnetic fluctuations are in fact responsible for the development ofsuperconducting order in other systems. Currently this debate is focused onseveral families of unconventional superconductors including high-Tc cuprates,borocarbides as well as heavy fermion systems where magnetism andsuperconductivity are known to coexist. Here we report a novel aspect ofcompetition and coexistence of these two competing orders in an interestingclass of heavy fermion compounds, namely the 1-1-5 series: CeTIn5 where T=Co,Ir, or Rh. Our optical experiments indicate the existence of regions inmomentum space where local moments remain unscreened. The extent of theseregions in momentum space appears to control both the normal andsuperconducting state properties in the 1-1-5 family of heavy fermion (HF)superconductors.