Direct observation of quasi-particle band in CeIrIn₅: Angle-resolved photoemission spectroscopy study

We have performed a high-resolution angle resolved Ce 4$d-4f$ resonant photoemission experiment on the heavy fermion superconductor CeIrIn$_5$. We have observed a quasi-particle band which has an energy dispersion of $\sim 30$ meV in the Ce 4$f$ on-resonance spectra. The result suggests that although the 4$f$ spectra are dominated by the localized/correlated character, the small itinerant component is responsible for the superconductivity in this compound.