Itinerant and local-moment magnetism in strongly correlated electron systems

TL;DR

This paper analyzes magnetic behaviors in the Hubbard model using DMFT, revealing how local-moment and itinerant magnetism dominate under different conditions and identifying re-entrant antiferromagnetic phases.

Contribution

It introduces a universal susceptibility expression within DMFT that distinguishes localized and itinerant magnetism in the Hubbard model.

Findings

Local-moment magnetism dominates at large Coulomb interactions.

Itinerant quasiparticle magnetism prevails at weak interactions.

Re-entrant antiferromagnetic behavior occurs at intermediate regimes.

Abstract

Detailed analysis of the magnetic properties of the Hubbard model within dynamical mean-field theory (DMFT) is presented. Using a RPA-like decoupling of two-particle propagators we derive a universal form for susceptibilities, which captures essential aspects of localized and itinerant pictures. This expression is shown to be quantitatively valid whenever long-range coherence of particle-hole excitations can be neglected, as is the case in large parts of the phase diagram where antiferromag- netism is dominant. The applicability of an interpretation in terms of the two archetypical pictures of magnetism is investigated for the Hubbard model on a body-centered cubic lattice with additional next-nearest neighbor hopping t'. For large values of the Coulomb interaction, local-moment mag- netism is found to be dominant, while for weakly interacting band electrons itinerant quasiparticle magnetism prevails. In the intermediate regime and for finite t' an re-entrant behavior is discovered, where antiferromagnetism only exists in a finite temperature interval.