Hubbard model calculations of phase separation in optical lattices

TL;DR

This paper uses the extended Hubbard model and advanced theoretical methods to predict phase separation phenomena in 2D optical lattices with ultracold Fermi atoms, highlighting conditions for various quantum phases.

Contribution

It introduces a detailed theoretical analysis of phase separation in 2D optical lattices using the extended Hubbard model and Gutzwiller projection, predicting phenomena relevant for ultracold atom experiments.

Findings

Phase separation occurs near half filling when U > 7.3t.

Discontinuous density distribution with Mott plateau in confined lattices.

Predicted phases include antiferromagnetic, Mott insulator, d-wave and gossamer superfluid.

Abstract

Antiferromagnetic, Mott insulator, d-wave and gossamer superfluid phases are calculated for 2D square lattices from the extended Hubbard (t-J-U) model using the Gutzwiller projection method and renormalized mean field theory. Phase separation between antiferromagnetic and d-wave superfluid phases is found near half filling when the on-site repulsion exceeds $U\ga7.3t$, and coincides with a first order transition in the double occupancy. Phase separation is thus predicted for 2D optical lattices with ultracold Fermi atoms whereas it is inhibited in cuprates by Coulomb frustration which instead may lead to stripes. In a confined optical lattice the resulting density distribution is discontinuous an with extended Mott plateau which enhances the antiferromagnetic phase but suppresses the superfluid phase. Observation of Mott insulator, antiferromagnetic, stripe and superfluid phases in density and momentum distributions and correlations is discussed.