Bethe-Ansatz solution of a model for a mixed valent impurity with two magnetic configurations: Groundstate and thermodynamics

We consider a mixed valence impurity with two magnetic configurations of spinJ ₂ andJ ₁=J ₂±1/2, respectively, coupled bys-wave conduction electrons via a hybridization matrix element. The model contains theU limit of the non-degenerate Anderson model and the Kondo exchange Hamiltonian for arbitrary spin as special cases. The model is solved by Bethe's ansatz and the groundstate and the thermodynamic properties are discussed. The Kondo limit and the highT perturbation expansion are extracted from the thermodynamic Bethe-ansatz equations. The ground state is magnetic if neitherJ ₁ norJ ₂ is a singlet.Heisenberg fellow of the Deutsche Forschungsgemeinschaft