Local-Ansatz Approach with Momentum Dependent Variational Parameters to Correlated Electron Systems

TL;DR

This paper introduces an improved wavefunction approach with momentum-dependent variational parameters for correlated electron systems, enhancing the local-ansatz method and accurately describing ground-state and excitation properties in the Hubbard model.

Contribution

It proposes a novel wavefunction that extends the local-ansatz method by incorporating momentum dependence, leading to better descriptions of correlated electron systems.

Findings

Improved ground-state energy calculations.

Realistic momentum distribution functions.

Quantitative description of excitation spectra and gap formation.

Abstract

A new wavefunction which improves the Gutzwiller-type local ansatz method has been proposed to describe the correlated electron system. The ground-state energy, double occupation number, momentum distribution function, and quasiparticle weight have been calculated for the half-filled band Hubbard model in infinite dimensions. It is shown that the new wavefunction improves the local-ansatz approach (LA) proposed by Stollhoff and Fulde. Especially, calculated momentum distribution functions show a reasonable momentum dependence. The result qualitatively differs from those obtained by the LA and the Gutzwiller wavefunction. Furthermore, the present approach combined with the projection operator method CPA is shown to describe quantitatively the excitation spectra in the insulator regime as well as the critical Coulomb interactions for a gap formation in infinite dimensions.