| speaker: | Friedrich Reinert Fachrichtung 7.2 - Experimentalphysik, Universität des Saarlandes, Saarbrücken, Germany |
| time: | Tu. 08.04.03, 14:30 - 15:20 |
The physical properties of a heavy Fermion system like CeCu2Si2 are closely related to the existence of a sharp feature in the electronic density of states close to the Fermi level. This feature is usually called the Kondo resonance, which can be explained as a consequence of the electron-electron scattering processes between conduction electrons and the localized electrons in the rare-earth f-orbitals. Unfortunately, this Kondo resonance combines two properties, that make a direct spectral investigation rather complicated: 1.) its position and line width is typically on a small energy scale - defined by the Kondo temperature TK - orders of magnitude below the energy resolution of Inverse Photoemission spectrometers. 2.) the maximum position lies above the Fermi level EF, usually out of the reach of photoemission spectroscopy, where the resolution is much better. However, this problem is - at least partly - solved by modern high-resolution photoemission spectrometers. The resulting data can be modeled by a numerical method based on the single impurity Anderson model (SIAM) in the non-crossing approximation (NCA) and gives experimental values for the Kondo temperature TK and the crystal field energies Delta(C.E.F.), which usually both are determined by inelastic neutron scattering. The excellent quantitative agreement between these two different experimental techniques on different gamma-Ce like compounds, and the consistent theoretical description - including the temperature dependence of the spectra - strongly indicate that the local picture of the SIAM is applicable to these systems.