Topological quantum phase transition between Fermi liquid phases in an Anderson impurity model

Abstract

We study a generalized Anderson model that mixes two localized configurations---one formed by two degenerate doublets and the other by a triplet with single-ion anisotropy $D{S}_{z}^{2}$---by means of two degenerate conduction channels. The model has been derived for a single Ni impurity embedded into an O-doped Au chain. Using the numerical renormalization group, we find a topological quantum phase transition, at a finite value ${D}_{c},$ between two regular Fermi liquid phases of high (low) conductance and topological number $2{I}_{L}/\ensuremath{\pi}=0$ (+1) for $D<{D}_{c}$ ($D>{D}_{c}$), where ${I}_{L}$ is the well-known Luttinger integral. At finite temperature the two phases are separated by a non-Fermi liquid phase with fractional impurity entropy $\frac{1}{2}\mathrm{ln}2$ and other properties which are similar to those of the two-channel Kondo model.