MAGNETIC IMPURITY IN A METAL WITH CORRELATED CONDUCTION ELECTRONS - AN INFINITE-DIMENSIONS APPROACH

We consider the Hubbard model with a magnetic Anderson impurity couple d to a lattice site. In the case of infinite dimensions, one-particle correlations of the impurity electron are described by the effective H amiltonian of the two-impurity system. One of the impurities interacts with a bath of free electrons and represents the Hubbard lattice, and the other is coupled to the first impurity by the bare hybridization interaction. A study of the effective two-impurity Hamiltonian in the frame of the 1/N expansion and for the case of a weak conduction-elect ron interaction (small U) reveals an enhancement of the usual exponent ial Kondo scale. However, an intermediate interaction (U/D = 1 - 3), t reated by the variational principle, leads to the loss of the exponent ial scale. The Kondo temperature T-K of the effective two-impurity sys tem is calculated as a function of the hybridization parameter, and it is shown that T-K decreases with an increase of U. The nonexponential scale of the Kondo effect in the intermediate regime at half-filling is discussed.