Effect of Cd- and Sn-doping in CeCoIn5 on the hybridization gap and f -electron amplitude studied with infrared spectroscopy

We investigated hole (Cd)- and electron (Sn)-doped CeCoIn₅ [CeCo(In_1-xTₓ)₅ (T=Cd or Sn)] using infrared spectroscopy. Doping-dependent hybridization-gap distribution functions were obtained from the optical conductivity spectra based on the periodic Anderson model formalism. The hybridization-gap distribution exhibits two components: in-plane and out-of-plane hybridization gaps. The doping-dependent evolution of the two gaps indicated that the out-of-plane gap was more sensitive to doping. Furthermore, the magnetic optical resistivity exhibited a doping-dependent evolution of the f-electron amplitude. The two dopant types exhibited different physical properties depending on the level of doping. The Sn dopant increases the f-electron amplitude, whereas the Cd dopant does not affect the f-electron amplitude. Doping-dependent effective mass is peaked at pure (or undoped) CeCoIn₅. Our spectroscopic results may help understand the doping-dependent electronic evolution of one of the canonical heavy-fermion systems, CeCoIn₅.