Momentum Dependent Local-Ansatz Wavefunction from Weak to Strong Electron Correlations

TL;DR

This paper introduces a modified momentum-dependent local-ansatz wavefunction that accurately describes electron correlations across weak to strong Coulomb interactions, improving upon previous models like the Gutzwiller wavefunction.

Contribution

The authors develop a new wavefunction combining the MLA with an alloy-analogy starting point, extending its applicability from intermediate to strong electron correlations.

Findings

The new wavefunction yields lower ground-state energy than the Gutzwiller wavefunction across all Coulomb regimes.

Double occupation number is reduced in the metallic regime and remains finite in the insulator regime.

Momentum distribution exhibits distinct, qualitatively different features from the Gutzwiller wavefunction.

Abstract

Momentum dependent local-ansatz (MLA) wavefunction describes accurately electron correlations from the weak to intermediate Coulomb interaction regimes. We point out that the MLA can describe the correlations from the weak to strong Coulomb interaction regimes by modifying the starting wavefunction from the Hartree-Fock (HF) type to an alloy-analogy (AA) type wavefunction. Numerical results based on the half-filled band Hubbard model on the hypercubic lattice in infinite dimensions show up that the new wavefunction yields the ground-state energy lower than the Gutzwiller wavefunction (GW) in the whole Coulomb interaction regime. Calculated double occupation number is smaller than the result of the GW in the metallic regime, and is finite in the insulator regime. Furthermore, the momentum distribution shows a distinct momentum-dependence in both the metallic and insulator regions, which are qualitatively different from those of the GW.