Equation of Motion Solutions to Hubbard Model retaining Kondo Effect

TL;DR

This paper introduces a novel equation of motion approach within DMFT to analyze the Hubbard model, successfully capturing the Kondo effect and quasiparticle resonance at finite Coulomb interactions.

Contribution

It develops a new EOM method differentiating over both times to retain the Kondo effect in Hubbard model analysis within DMFT.

Findings

Reproduces the three-peak DOS structure with Hubbard bands and quasiparticle peak.

Maintains constant quasiparticle peak height at zero temperature for small Coulomb interactions.

Aligns with full DMFT results from Quantum Monte Carlo and perturbation theory.

Abstract

We propose a new way of analyzing the Hubbard model using equations of motion (EOM) for the higher-order Green's functions approach within the DMFT scheme. In calculating the higher order Green function we will differentiate over both Times (t) and (t'). This allows us to obtain the metallic Fermi liquid at nonzero Coulomb interaction, where the three center density of states (DOS) structure with two Hubbard bands and the quasiparticle resonance peak is obtained. At small Coulomb interactions and zero temperature the height of the quasiparticle resonance peak on the Fermi energy is constant similarly as in the full DMFT method with numerical (Quantum Monte Carlo) or with analytical (e.g. iterative perturbation theory) calculations.