Spin frustration of a spin-1/2 Ising-Heisenberg three-leg tube as an indispensable ground for thermal entanglement

TL;DR

This paper exactly solves a spin-1/2 Ising-Heisenberg three-leg tube model, revealing that spin frustration is essential for thermal entanglement and showing complex thermal behaviors including sharp specific heat peaks.

Contribution

It provides an exact solution of the model and demonstrates the crucial role of spin frustration in enabling thermal entanglement and complex thermal properties.

Findings

Spin frustration is essential for thermal entanglement.

The model exhibits a sharp low-temperature peak in specific heat.

Thermal excitations lead to high degeneracy and anomalous thermal behavior.

Abstract

The spin-1/2 Ising-Heisenberg three-leg tube composed of the Heisenberg spin triangles mutually coupled through the Ising inter-triangle interaction is exactly solved in a zero magnetic field. By making use of the local conservation for the total spin on each Heisenberg spin triangle the model can be rigorously mapped onto a classical composite spin-chain model, which is subsequently exactly treated through the transfer-matrix method. The ground-state phase diagram, correlation functions, concurrence, Bell function, entropy and specific heat are examined in detail. It is shown that the spin frustration represents an indispensable ground for a thermal entanglement, which is quantified with the help of concurrence. The specific heat displays diverse temperature dependences, which may include a sharp low-temperature peak mimicking a temperature-driven first-order phase transition. It is convincingly evidenced that this anomalous peak originates from massive thermal excitations from the doubly degenerate ground state towards an excited state with a high macroscopic degeneracy due to chiral degrees of freedom of the Heisenberg spin triangles.