title: Studying quantum spin systems through entanglement estimators.
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 multispin 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.
authors.affiliation: Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089-0484, USA.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Roscilde
authors.forename: Paola
authors.initials: P
authors.lastname: Verrucchi
authors.forename: Andrea
authors.initials: A
authors.lastname: Fubini
authors.forename: Stephan
authors.initials: S
authors.lastname: Haas
authors.forename: Valerio
authors.initials: V
authors.lastname: Tognetti