Temperature Dependence of the 4 <i>f</i> Spectral Function in the Kondo System CeSi ₂ : Evidence of the Kondo Resonance Smearing

Abstract

High-resolution photoemission (UPS) and bremsstrahlung isochromat spectra (BIS) have been measured as a function of temperature in CeSi2. In UPS measurements, owing to the high resolution, a weak-temperature evolution can be observed whereas a large effect is shown in BIS. In both cases, the temperature dependence of the spectral function reflects the breakdown of the Kondo state as the low-lying magnetic states become thermally populated. Although the energy resolution of BIS is one order of magnitude larger than the thermodynamic energy scale (the Kondo energy), a significant temperature dependence is observed in BIS spectra.