Phase transitions in exactly solvable decorated model of localized Ising spins and itinerant electrons

TL;DR

This paper presents an exact solution for a hybrid lattice model combining localized Ising spins and itinerant electrons, revealing phase transitions and magnetic ordering depending on interaction ratios.

Contribution

It introduces an exactly solvable decorated lattice model with mixed localized and itinerant spins, analyzing phase behavior and critical temperatures.

Findings

Ground state can be ferromagnetic or ferrimagnetic depending on interactions.

Critical temperature increases with the kinetic to exchange interaction ratio.

Model exhibits phase transitions driven by interaction parameters.

Abstract

A hybrid lattice-statistical model of doubly decorated two-dimensional lattices, which have localized Ising spins at its nodal sites and itinerant electrons delocalized over decorating sites, is exactly solved with the help of a generalized decoration-iteration transformation. Under the assumption of a quarter filling of each couple of the decorating sites, the ground state constitutes either spontaneously long-range ordered ferromagnetic or ferrimagnetic phase in dependence on whether the ferromagnetic or antiferromagnetic interaction between the localized Ising spins and itinerant electrons is considered. The critical temperature of the spontaneously long-range ordered phases monotonically increases upon strengthening the ratio between the kinetic term and the Ising-type exchange interaction.