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

TL;DR

This paper introduces a hybrid wavefunction within the momentum dependent local-ansatz framework, improving ground-state energy calculations across weak to strong electron correlations in the Hubbard model.

Contribution

It develops a flexible hybrid wavefunction that interpolates between Hartree-Fock and alloy-analogy types, enhancing the variational approach for correlated electrons.

Findings

Lower ground-state energy than Gutzwiller wavefunction across all Coulomb interactions

Smaller double occupation number in weak interaction regime

Distinct momentum dependence in the distribution

Abstract

The variational theory of momentum dependent local-ansatz (MLA) has been generalized by introducing a hybrid (HB) wavefunction as a starting wavefunction, whose potential can flexibly change from the Hartree-Fock type to the alloy-analogy type by varying a weighting factor from zero to one. 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 that of the Gutzwiller wavefunction (GW) in the whole Coulomb interaction regime. Calculated double occupation number is smaller than the result of the GW in the weak Coulomb interaction regime, and remains finite in the strong regime. Furthermore, the momentum distribution shows a distinct momentum dependence, which is qualitatively different from that of the GW.