Development of an efficient impurity solver in dynamical mean field theory for multi-band systems: The iterative perturbation theory combined with the parquet equations

TL;DR

This paper introduces an improved impurity solver for multi-band dynamical mean field theory by combining iterative perturbation theory with parquet equations, enhancing efficiency and reliability.

Contribution

The authors develop a novel impurity solver that integrates IPT with parquet equations, providing a more accurate and computationally efficient approach for multi-band systems.

Findings

Good agreement with continuous-time quantum Monte Carlo results

Enhanced efficiency and reliability in impurity solving

Applicable to various models in DMFT

Abstract

Although several impurity solvers in the dynamical mean field theory (DMFT) have been proposed, especially in multi-band systems, there are practical difficulties arising from a trade-off between numerical costs and reliability. In this study, we re-interpret the iterative perturbation theory (IPT) as an approximation which captures the strong correlation effects by mimicking the particular frequency structures of the exact full vertex, and extend it such that it can have efficiency and reliability simultaneously by modifying IPT vertex using the parquet equations. We apply this method to several models to evaluate their validity. We confirm that our method shows good agreements with the numerically exact continuous-time quantum Monte Carlo method in the single-site DMFT calculation.