Thermal entanglement in an orthogonal dimer-plaquette chain with alternating Ising-Heisenberg coupling

TL;DR

This paper investigates quantum entanglement in an infinite orthogonal dimer-plaquette Ising-Heisenberg chain, revealing its phase diagram, thermodynamic properties, and thermal entanglement behavior, including reentrant phenomena and threshold temperatures.

Contribution

It introduces an exact solution for the entanglement properties of an orthogonal dimer-plaquette chain using gauge symmetry and transformation techniques, highlighting novel entanglement features.

Findings

Identified five ground states including ferromagnetic, antiferromagnetic, and disordered phases.

Analyzed the residual entropy and thermodynamic properties of the model.

Discovered reentrant threshold temperatures for thermal entanglement in dimers.

Abstract

In this paper we explore the entanglement in orthogonal dimer-plaquette Ising-Heisenberg chain, assembled between plaquette edges, also known as orthogonal dimer plaquettes. The quantum entanglement properties involving an infinite chain structure are quite important, not only because the mathematical calculation is cumbersome but also because real materials are well represented by infinite chain. Using the local gauge symmetry of this model, we are able to map onto a simple spin-1 like Ising and spin-1/2 Heisenberg dimer model with single effective ion anisotropy. Thereafter this model can be solved using the decoration transformation and transfer matrix approach. First, we discuss the phase diagram at zero temperature of this model, where we find five ground states, one ferromagnetic, one antiferromagnetic, one triplet-triplet disordered and one triplet-singlet disordered phase, beside a dimer ferromagnetic-antiferromagnetic phase. In addition, we discuss the thermodynamic properties such as entropy, where we display the residual entropy. Furthermore, using the nearest site correlation function it is possible also to analyze the pairwise thermal entanglement for both orthogonal dimers, additionally we discuss the threshold temperature of the entangled region as a function of Hamiltonian parameters. We find quite interesting thin reentrance threshold temperature for one of the dimers, and we also discuss the differences and similarities for both dimers.