On the density of states for the Hubbard model: pseudo-particle Keldysh diagram method - an alternative to DMFT?

TL;DR

This paper introduces a Keldysh diagram technique for the Hubbard model that incorporates nonlocal effects, providing an alternative to DMFT and addressing the artificial central peak issue in density of states calculations.

Contribution

It develops a self-consistent pseudo-particle Keldysh diagram method including nonlocal effects, offering a new approach to study the Hubbard model beyond DMFT.

Findings

Elimination of the artificial Kondo-like peak in the density of states.

Analysis of density of states variations with Coulomb U and electron concentration.

Demonstration of nonlocal effects in 2D Hubbard model calculations.

Abstract

It is shown how to construct Keldysh diagram technique for pseudo - particle approach to the Hubbard model. We propose self consistent equations for pseudo particle and electron Green functions in Keldysh diagram technique. Nonlocal effects (spatial dispersion) are included in single impurity problem in this method. Thus we can get rid of the artificial central peak (of Kondo type) in the density of states which is inevitable in Dynamical Mean Field Theory (DMFT). The changes in the density of states for 2D Hubbard model due to variation of Coulomb repulsion U and electron concentration are analyzed.