Temperature-invariant photoelectron spectra in cerium heavy-fermion compounds: Inconsistencies with the Kondo model

Abstract

4f levels in Ce heavy-fermion compounds are examined using resonant photoemission. We find the following inconsistencies with the predictions of the Kondo model: (a) All temperature dependence can be accounted for simply by phonon broadening and the Fermi function; (b) the spectral weights of the features near ${\mathit{E}}_{\mathit{F}}$ do not scale with ${\mathit{T}}_{\mathit{K}}$; and (c) the line shape of the feature previously identified as the Kondo resonance is Lorentzian and about an order of magnitude broader than predictions. Instrument resolution is not a limiting factor.