Enhancement of pairwise entanglement from $\mathbbm{Z}_2$ symmetry breaking

TL;DR

This paper investigates how symmetry breaking during quantum phase transitions can enhance pairwise entanglement in spin-1/2 models, highlighting conditions under which entanglement remains unchanged or is increased due to strong correlations.

Contribution

It identifies specific correlation function conditions that determine whether symmetry breaking affects pairwise entanglement, revealing that strong correlations can lead to entanglement enhancement.

Findings

Mean-field models maintain entanglement despite symmetry breaking

Strongly correlated models can exhibit entanglement enhancement

Two examples demonstrate order-induced entanglement increase

Abstract

We study the effect of symmetry breaking in a quantum phase transition on pairwise entanglement in spin-1/2 models. We give a set of conditions on correlation functions a model has to meet in order to keep the pairwise entanglement unchanged by a parity symmetry breaking. It turns out that all mean-field solvable models do meet this requirement, whereas the presence of strong correlations leads to a violation of this condition. This results in an order-induced enhancement of entanglement, and we report on two examples where this takes place.