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 DSz2-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 Dc, between two regular Fermi liquid phases of high (low) conductance and topological number 2IL/π=0 (+1) for D Dc), where IL is the well-known Luttinger integral. At finite temperature the two phases are separated by a non-Fermi liquid phase with fractional impurity entropy 12ln2 and other properties which are similar to those of the two-channel Kondo model.