Münster 1999 – scientific programme

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TT: Tiefe Temperaturen

TT 22: Quantenstörstellen und quantenkritische Ph
änomene

TT 22.2: Invited Talk

Friday, March 26, 1999, 10:00–10:30, F3

Fermi and Non-Fermi Liquid Behavior in Quantum Impurity Systems: Conserving Slave Boson Theory — •J. Kroha — Institut für Theorie der Kondensierten Materie, Universität Karlsruhe, D-76128 Karlsruhe, Germany

The unusual low-temperture properties observed in a large number of correlated electron systems with strong, short-range repulsion, including non-Fermi liquid behavior, calls for the development of new many-body techniques to describe such systems. As a standard model which, depending on the symmetry, contains Fermi as well as non-Fermi liquid behavior, we consider the SU(N) x SU(M) Anderson impurity model. A conserving auxiliary particle theory is shown to account for the strong correlations governing the system in a controlled way, preserving the local conservation laws. Coherent spin flip as well as charge fluctuation processes are included on the level of a conserving T-matrix approximation (CTMA). It is proved by means of a cancellation theorem that this incorporates all leading and subleading infrared singular contributions at any given order in a selfconsistent loop expansion for this problem. As a result, the CTMA correctly describes the infrared behavior of physical quantities both in the Fermi and the non-Fermi regimes of the Anderson model. Extensions of the theory to lattice problems are discussed.