Fermi and non-Fermi liquid behavior in quantum impurity systems: Conserving slave boson theory

Abstract

The question of Fermi liquid vs. non-Fermi liquid behavior induced by strong correlations is one of the prominent problems in metallic local moment systems. As standard models for such systems, the SU(N)xSU(M) Anderson impurity models exhibit both Fermi liquid and non-Fermi liquid behavior, depending on their symmetry. Taking the Anderson model as an example, these lectures first give an introduction to the auxiliary boson method to describe correlated systems governed by a strong, short-range electronic repulsion. It is then shown how to include the relevant low-lying excitations (coherent spin flip and charge fluctuation processes), while preserving the local gauge symmetry of the model. This amounts to a conserving T-matrix approximation (CTMA). We prove a cancellation theorem showing that the CTMA incorporates all leading and subleading infrared singularities at any given order in a self-consistent loop expansion of the free energy. As a result, the CTMA recovers the correct infrared behavior of the auxiliary particle propagators, indicating that it correctly describes both the Fermi and the non-Fermi regimes of the Anderson model.

37 pages, LaTeX, style file included, 10 postscript figures; to appear in Proceedings of the XXXVIII Cracow School of Theoretical Physics, Zakopane, Poland, June 1-10, 1998

References in corpus (3)

• Spin-Flavor Separation and Non-Fermi Liquid Behavior in the Multichannel Kondo Problem: A Large N Approach
• Unified description of Fermi and non-Fermi liquid behavior in a conserving slave boson approximation for strongly correlated impurity models
• Numerical Renormalization Group Study of Pseudo-Fermion and Slave-Boson Spectral Functions in the Single Impurity Anderson Model

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• Improved strong-coupling perturbation theory of the symmetric Anderson impurity model
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