Physics – Condensed Matter – Strongly Correlated Electrons
Scientific paper
2004-10-12
J. Phys. Soc. Jpn. 74, 16 (2005)
Physics
Condensed Matter
Strongly Correlated Electrons
10 pages, invited article, to appear in a special edition of JPSJ "Kondo Effect - 40 Years after the Discovery", published ver
Scientific paper
10.1143/JPSJ.74.16
Self-consistent diagrammatic approximations to the Anderson or Kondo impurity model, using an exact pseudoparticle representation of the impurity states, are reviewed. We first discuss the infrared exponents of the pseudoparticle propagators as indicators of Fermi liquid behavior through their dependence on the impurity occupation and on magnetic field. Then we discuss the Non-Crossing Approximation (NCA), identifying its strengths, but also its fundamental shortcomings. Physical arguments as well as a perturbative renormalization group analysis suggest that an infinite parquet-type resummation of two-particle vertex diagrams, the Conserving T-Matrix Approximation (CTMA) will cure the deficiencies of NCA. We review results on the pseudoparticle spectral functions, the spin susceptibility and the impurity electron spectral function, supporting that the CTMA provides qualitatively correct results, both in the high-temperature regime and in the strong coupling Fermi liquid regime at low temperatures.
Kroha Johann
W"olfle Peter
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