Gunnarsson O., Schonhammer K.
Spectroscopic and thermodynamic properties of Ce mixed valence compounds are studied for the Anderson model. The large orbital and spin degeneracy Nf of the f-level allows the authors to treat 1/Nf as a small parameter. In this way exact results can be obtained for Nf= infinity and T=0, and even for Nf=1 or 2 accurate results are obtained if corrections of order 1/Nf are considered. Comparison between theory and experiment for core level X-ray photoemission spectra leads to estimates of the parameters in the model. With these parameters the model can also give a fairly good description of other spectroscopies, such as M4,5XAS, 4f PES and BIS. The values of the parameters place the known Ce intermetallics in or close to the Kondo limit. In this limit the f-spectral function has a narrow Kondo resonance close to the Fermi energy, which has been seen spectroscopically for some of the systems. This resonance is related to a large density of low-lying excitations, which explains the large low temperature susceptibility and specific heat of these systems.
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