Rise and Fall of Reentrant Phase Transitions in a Coupled Spin-Electron Model on a Doubly Decorated Honeycomb Lattice

TL;DR

This paper rigorously analyzes a coupled spin-electron model on a doubly decorated honeycomb lattice, revealing complex phase behavior including reentrant transitions influenced by electron filling, hopping, and spin couplings.

Contribution

It provides a detailed phase diagram and magnetization analysis for a quantum spin-electron model, highlighting the impact of further-neighbor interactions on reentrant phase transitions.

Findings

Identification of ferromagnetic, antiferromagnetic, and paramagnetic phases.

Reentrant phase transitions are affected by further-neighbor Ising coupling.

Phase boundaries depend on electron filling, hopping, and coupling constants.

Abstract

Phase diagrams and spontaneous magnetization are rigorously calculated for a coupled spin-electron model on a doubly decorated honeycomb lattice, which accounts for a quantum-mechanical hopping of the mobile electrons on decorating sites, the nearest-neighbor Ising coupling between mobile electrons and localized spins, as well as, the further-neighbor Ising coupling between the localized spins placed on nodal sites. The spontaneously ordered ferromagnetic phase, spontaneously ordered antiferromagnetic phase and disordered paramagnetic phase emerge in a phase diagram depending on an electron filling of the decorating sites, a relative size of the hopping term and both considered coupling constants. It is evidenced that a nature and size of the further-neighbor Ising coupling between the localized spins basically influences rise and fall of reentrant transitions close to a phase boundary between the paramagnetic phase and both spontaneously ordered phases.