Entanglement in the Majumdar-Ghosh model

TL;DR

This paper investigates the entanglement properties of the Majumdar-Ghosh model, revealing how entanglement entropy deviations signal the dimer phase transition at a specific coupling ratio.

Contribution

It provides the first detailed analysis of entanglement entropy behavior in the Majumdar-Ghosh model near the phase transition point.

Findings

Entanglement entropy deviates from unfrustrated chain behavior when J2 > 0.25

Deviation signals the dimer phase transition at J2* ≈ 0.2411 J1

Entanglement at the Majumdar-Ghosh point J2=0.5 J1 analyzed

Abstract

We present an analysis of the entanglement characteristics in the Majumdar-Ghosh (MG) or $J_{1}$-$J_{2}$ Heisenberg model. For a system consisting of up to 28 spins, there is a deviation from the scaling behaviour of the entanglement entropy characterizing the unfrustrated Heisenberg chain as soon as $J_{2} >0.25$. This feature can be used as an indicator of the dimer phase transition that occurs at $J_{2} = J_{2}^{*} \approx 0.2411 J_{1}$. Additionally, we also consider entanglement at the MG point $J_{2}=0.5 J_{1}$.