Orbital order in degenerate Hubbard models : A variational study

TL;DR

This paper employs Gutzwiller variational theory to study orbital order in a two-band Hubbard model, revealing that orbital order is much more limited in parameter space than previously suggested by Hartree-Fock methods.

Contribution

It provides a more accurate variational analysis showing the restricted stability of orbital order compared to earlier Hartree-Fock predictions.

Findings

Orbital order exists only near half filling in the Gutzwiller approach.

Hartree-Fock predicts a wide range of orbital orders, unlike the Gutzwiller results.

Gutzwiller theory offers a refined understanding of orbital stability in Hubbard models.

Abstract

We use the Gutzwiller variational many-body theory to investigate the stability of orbitally ordered states in a two-band Hubbard-model without spin degrees of freedom. Our results differ significantly from earlier Hartree-Fock calculations for this model. The Hartree-Fock phase diagram displays a large variety of orbital orders. In contrast, in the Gutzwiller approach orbital order only appears for densities in a narrow region around half filling.