Studying quantum spin systems through entanglement estimators

TL;DR

This paper investigates how entanglement measures in anisotropic quantum spin chains change with magnetic field, revealing abrupt transitions and a new entanglement-based method to detect quantum phase transitions.

Contribution

It introduces a novel approach using entanglement estimators to identify quantum phase transitions in spin systems through Quantum Monte Carlo simulations.

Findings

Entanglement vanishes below critical field and recovers after the transition.

A deep minimum in the entanglement ratio signals the quantum critical point.

Entanglement estimators provide a new way to detect phase transitions.

Abstract

We study the field dependence of the entanglement of formation in anisotropic S=1/2 antiferromagnetic chains displaying a T=0 field-driven quantum phase transition. The analysis is carried out via Quantum Monte Carlo simulations. At zero temperature the entanglement estimators show abrupt changes at and around criticality, vanishing below the critical field, in correspondence with an exactly factorized state, and then immediately recovering a finite value upon passing through the quantum phase transition. At the quantum critical point, a deep minimum in the pairwise-to-global entanglement ratio shows that multi-spin entanglement is strongly enhanced; moreover this signature represents a novel way of detecting the quantum phase transition of the system, relying entirely on entanglement estimators.