MAGNETIC, NONMAGNETIC, AND NON-FERMI-LIQUID GROUND-STATE OF AN IMPURITY FLUCTUATING BETWEEN 2 MAGNETIC CONFIGURATIONS

The ground state of a generalized Anderson model for valence fluctuations between two magnetic p, d, or f configurations is discussed. In the isotropic limit, in contrast to the ordinary Anderson model, the localized problem (limit of zero bandwidth) does not correspond to a stable fixed point, except in the extreme case of j-j coupling. Taking the simplest possible case (fluctuations between p(4) and p(3) or p(5)) under a tetragonal (C-4 nu) crystal field, depending on the retained low-energy multiplets, the model can be mapped into an ordinary Anderson model, another model with a magnetic ground state, and for particular parameters, a two-channel Kondo model.