Strong Coupling Solver for the Quantum Impurity Model

TL;DR

This paper introduces a rapid impurity solver based on atomic limit perturbation theory, effective for DMFT calculations, especially in Mott insulators and magnetic phase transitions, aligning well with established methods.

Contribution

The paper presents a novel, fast impurity solver for quantum impurity models that performs well in Mott insulators and magnetic transitions, enhancing LDA+DMFT studies.

Findings

Works well in paramagnetic Mott insulator phase

Accurately predicts Neel temperature in large U limit

Agrees with QMC results for phase transition

Abstract

We propose a fast impurity solver for the general quantum impurity model based on the perturbation theory around the atomic limit, which can be used in combination with the local density approximation (LDA) and the dynamical mean field theory (DMFT). We benchmark the solver in the two band Hubbard model within DMFT against quantum Monte Carlo (QMC) and numerical renormalization group (NRG) results. We find that the solver works very well in the paramagnetic Mott insulator phase. We also apply this impurity solver to the DMFT study of the anti-ferromagnetic phase transition in the unfrustrated Bethe lattice. The Neel temperature obtained by the fast impurity solver agrees very well with the QMC results in the large Hubbard U limit. The method is a promising tool to be used in combination with the LDA+DMFT to study Mott insulators starting from first principles.