Magnetic impurity in a metal with correlated conduction electrons: An infinite-dimensions approach

We consider the Hubbard model with a magnetic Anderson impurity coupled to a lattice site. In the case of infinite dimensions, one-particle correlations of the impurity electron are described by the effective Hamiltonian 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 (Formula presented) expansion and for the case of a weak conduction-electron interaction (small (Formula presented)) reveals an enhancement of the usual exponential Kondo scale. However, an intermediate interaction (Formula presented) treated by the variational principle, leads to the loss of the exponential scale. The Kondo temperature (Formula presented) of the effective two-impurity system is calculated as a function of the hybridization parameter, and it is shown that (Formula presented) decreases with an increase of (Formula presented) The nonexponential scale of the Kondo effect in the intermediate regime at half-filling is discussed.