A Standard Basis Operator Equation of Motion Impurity Solver for Dynamical Mean Field Theory

TL;DR

This paper introduces an efficient impurity solver for dynamical mean-field theory that combines exact diagonalization for low-energy states with Green's function approximation for high-energy states, improving computational efficiency.

Contribution

The paper develops a novel impurity solver using a standard basis operator formalism that coherently integrates exact and approximate methods for DMFT applications.

Findings

Qualitative agreement with established methods for the Anderson impurity model.

Effective combination of exact diagonalization and Green's function approximation.

Potential for improvements and promising features discussed.

Abstract

We present an efficient impurity solver for the dynamical mean-field theory (DMFT). It is based on the separation of bath degrees of freedom into the low energy and the high energy parts. The former is solved exactly using exact diagonalization and the latter is treated approximately using Green's function equation of motion decoupling approximation. The two parts are combined coherently under the standard basis operator formalism. The impurity solver is applied to the Anderson impurity model and, combined with DMFT, to the one-band Hubbard model. Qualitative agreement is found with other well established methods. Some promising features and possible improvements of the present solver are discussed.