Quantum Phase Transitions in the Bosonic Single-Impurity Anderson Model

TL;DR

This paper investigates a bosonic impurity model coupled to a bosonic bath, revealing a phase diagram with Mott and Bose-Einstein condensed phases separated by quantum critical points, with implications for quantum dots and Bose-Hubbard systems.

Contribution

It introduces a detailed analysis of the bosonic single-impurity Anderson model, highlighting its phase diagram and potential physical realizations, extending understanding of quantum impurity systems.

Findings

Identification of Mott and Bose-Einstein condensed phases

Discovery of quantum critical points separating phases

Relevance to atomic quantum dots and Bose-Hubbard models

Abstract

We consider a quantum impurity model in which a bosonic impurity level is coupled to a non-interacting bosonic bath, with the bosons at the impurity site subject to a local Coulomb repulsion U. Numerical renormalization group calculations for this bosonic single-impurity Anderson model reveal a zero-temperature phase diagram where Mott phases with reduced charge fluctuations are separated from a Bose-Einstein condensed phase by lines of quantum critical points. We discuss possible realizations of this model, such as atomic quantum dots in optical lattices. Furthermore, the bosonic single-impurity Anderson model appears as an effective impurity model in a dynamical mean-field theory of the Bose-Hubbard model.