Exact evidence for the spontaneous antiferromagnetic long-range order in the two-dimensional hybrid model of localized Ising spins and itinerant electrons

TL;DR

This paper provides an exact analysis of a two-dimensional hybrid model with localized spins and itinerant electrons, revealing spontaneous antiferromagnetic order and a non-monotonic critical temperature dependence.

Contribution

It introduces an exact solution for a hybrid lattice model combining Ising spins and itinerant electrons, highlighting quantum effects on magnetic order.

Findings

Spontaneous antiferromagnetic long-range order observed

Quantum reduction of staggered magnetization

Critical temperature shows non-monotonic behavior

Abstract

The generalized decoration-iteration transformation is adopted to treat exactly a hybrid model of doubly decorated two-dimensional lattices, which have localized Ising spins at their nodal lattice sites and itinerant electrons delocalized over pairs of decorating sites. Under the assumption of a half filling of each couple of the decorating sites, the investigated model system exhibits a remarkable spontaneous antiferromagnetic long-range order with an obvious quantum reduction of the staggered magnetization. It is shown that the critical temperature of the spontaneously long-range ordered quantum antiferromagnet displays an outstanding non-monotonic dependence on a ratio between the kinetic term and the Ising-type exchange interaction.