Non-Fermi-liquid behavior in an extended Anderson model.

An extended Anderson model, including screening channels (nonhybridizing, but interacting with the local orbit), is studied within the Anderson-Yuval approach, originally devised for the single-channel Kondo problem. By comparing the perturbation expansions of this model and a generalized resonant level model, the spin-spin correlation functions are calculated which show non-Fermi liquid exponent depending on the strength of the scattering potential. The relevance of this result to experiments in some heavy fermion systems is briefly discussed. 75.20.Hr, 75.30.Mb, 71.28.+d, 71.27.+a Typeset using REVTEX 1