Spectral Density of the Two-Impurity Anderson Model

TL;DR

This study uses the dynamical density-matrix renormalization group to analyze the ground-state properties of the two-impurity Anderson model, revealing quantum phase transitions driven by charge and magnetic correlations.

Contribution

It provides new insights into the mechanisms behind quantum phase transitions in the two-impurity Anderson model, emphasizing the role of effective exchange interactions.

Findings

Identifies a charge-driven quantum phase transition in the weak-coupling regime.

Shows magnetic correlation competition influences the transition at large Coulomb repulsion.

Suggests effective exchange interactions are key to the transition, contrasting phenomenological models.

Abstract

We investigate static and dynamical ground-state properties of the two-impurity Anderson model at half filling in the limit of vanishing impurity separation using the dynamical density-matrix renormalization group method. In the weak-coupling regime, we find a quantum phase transition as function of inter-impurity hopping driven by the charge degrees of freedom. For large values of the local Coulomb repulsion, the transition is driven instead by a competition between local and non-local magnetic correlations. We find evidence that, in contrast to the usual phenomenological picture, it seems to be the bare effective exchange interactions which trigger the observed transition.