Stability of Nagaoka phase, spin effective action and delocalized free holes

TL;DR

This paper investigates the stability of Nagaoka's ferromagnetic phase in the infinite-U Hubbard model using a slave fermion approach, analyzing how hole doping affects magnetic order and phase stability.

Contribution

It introduces a spin effective action framework to study the stability of Nagaoka's phase under finite hole doping in the Hubbard model.

Findings

Nagaoka's phase can be stable with finite hole doping depending on hopping treatment.

Delocalization of holes influences magnetic ordering.

Theoretical analysis of phase stability in strongly correlated electrons.

Abstract

The Hubbard model in the limit of infinite $U$ is investigated within a projected slave fermion representation and following a previous work of the author and collaborators \cite{BFK}. The stability of the Nagaoka's phase with respect to a non vanishing concentration of holes ($\delta_h$) is analyzed by envisaging the existence of a spin effective action for itinerant magnetism of the Hubbard model. It is considered that,as the hole doping increases away from the half filled insulating limit, free holes are expected to be more delocalized. Depending on treatment for the hopping: a ferromagnetic or anti-ferromagnetic ordering might arise and the Nagaoka's phase might have some stability with respect to $\delta_h \neq 0$.