Hybridization effects in CeCoIn5 observed by angle-resolved photoemission

We have investigated the low-energy electronic structure of the heavy fermion superconductor CeCoIn5 by angle-resolved photoemission. We focus on the dispersion and the peak width of the prominent quasi-two-dimensional Fermi surface sheet at the corner of the Brillouin zone as a function of temperature along certain k directions with a photon energy of h nu=100 eV. We find slight changes of the Fermi vector and an anomalous broadening of the peak width when the Fermi energy is approached. Additionally, we performed resonant angle-resolved photoemission spectroscopy experiments with h nu=121 eV. A flat f-derived band is observed with a distinct temperature dependence and a k-dependent spectral weight. These results, including both off- and on-resonant measurements, fit qualitatively to a two-level mixing model derived from the periodic Anderson model.