From Fermi-liquid-like to non-Fermi-liquid behavior of the generalized Anderson impurity model: The Bethe-ansatz solution

The exact solution for the generalized Anderson impurity model is presented. Here localized electrons interact in the shell via a Hubbard-like repulsion and Hund's rule exchange interaction. An impurity reveals, in general, a mixed-valent behavior. Depending on the relative position of the impurity level and the strengths of Hubbard like and Hund's couplings, an impurity can reveal either a Fermi-liquid-like or non-Fermi-liquid-like behavior. The competition between characteristics of in-shell Coulomb interactions can produce a behavior similar to the channel-anisotropic multichannel Kondo situation, which is responsible for the non-Fermi-liquid physics of the model. Similar conclusions can be made for a two-impurity Kondo model.