Local Order and the gapped phase of the Hubbard model: a plaquette dynamical mean field investigation

TL;DR

This study uses a four-site dynamical cluster approximation to explore the metal-insulator transition in the Hubbard model, revealing a potential energy-driven gap associated with antiferromagnetic correlations and a pseudogap phase upon doping.

Contribution

It demonstrates that the gapped phase in the Hubbard model is better described as a Slater phenomenon driven by short-range order, using a plaquette dynamical mean field approach.

Findings

Gap opens at critical interaction strength.

Gapped phase linked to antiferromagnetic and singlet correlations.

Doped phase exhibits pseudogap and non-Fermi-liquid behavior.

Abstract

The four-site DCA method of including intersite correlations in the dynamical mean field theory is used to investigate the metal-insulator transition in the Hubbard model. At half filling a gap-opening transition is found to occur as the interaction strength is increased beyond a critical value. The gapped behavior found in the 4-site DCA approximation is shown to be associated with the onset of strong antiferromagnetic and singlet correlations and the transition is found to be potential energy driven. It is thus more accurately described as a Slater phenomenon (induced by strong short ranged order) than as a Mott phenomenon. Doping the gapped phase leads to a non-Fermi-liquid state with a Fermi surface only in the nodal regions and a pseudogap in the antinodal regions at lower dopings $x \lesssim 0.15$ and to a Fermi liquid phase at higher dopings.