Global quantum correlations in finite-size spin chains

TL;DR

This paper investigates how global quantum correlations, measured by global discord, can detect critical points in finite-size quantum spin chains at finite temperature, revealing universal scaling behaviors.

Contribution

It demonstrates that global discord effectively signals criticality in various spin models, including the Ising and cluster-Ising models, even away from ground states.

Findings

Global discord detects critical points in finite-size systems.

Universal scaling of global discord observed in the Ising model.

Global discord is sensitive to quantum phase transitions at finite temperature.

Abstract

We perform an extensive study of the properties of global quantum correlations in finite-size one-dimensional quantum spin models at finite temperature. By adopting a recently proposed measure for global quantum correlations [C. C. Rulli, and M. S. Sarandy, Phys. Rev. A, 84, 042109 (2011)], called global discord, we show that critical points can be neatly detected even for many-body systems that are not in their ground state. We consider the transverse Ising model, the cluster-Ising model where three-body couplings compete with an Ising-like interaction, and the nearest-neighbor XX Hamiltonian in transverse magnetic field. These models embody our canonical examples showing the sensitivity of global quantum discord close to criticality. For the Ising model, we find a universal scaling of global discord with the critical exponents pertaining to the Ising universality class.