Multi-orbital Anderson models and the Kondo effect: a NCA study enhanced by vertex corrections |
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Authors: | N Grewe T Jabben and S Schmitt |
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Institution: | 1.Institut für Festk?rperphysik, Technische Universit?t Darmstadt,Darmstadt,Germany |
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Abstract: | The low energy region of certain transition metal compounds reveals dramatic correlation effects between electrons, which
can be studied by photoelectron spectroscopy. Theoretical investigations are often based on multi-orbital impurity models,
which exhibit modified versions of the Kondo effect. We present a systematic study of a multi-orbital Anderson-like model,
based on a new semi-analytical impurity solver which goes beyond simple modifications of the well known NCA. We discuss one-particle
excitation spectra and in particular the role of level positions and Coulomb-matrix elements. It is shown that the low-energy
region as well as the overall features of spectra critically depend on the model parameters and on the quality of the approximations
used. Recent photoelectron experiments and corresponding existing calculations are put into perspective. An interesting crossover
scenario between different regimes of ground states with characteristically different local correlations is uncovered. |
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Keywords: | PACS" target="_blank">PACS 71 10 -w Theories and models of many-electron systems 71 20 -b Electron density of states and band structure of crystalline solids 71 27 +a Strongly correlated electron systems heavy fermions 71 55 -i Impurity and defect levels |
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