title: Entanglement and factorized ground states in two-dimensional quantum antiferromagnets.
abstract: Making use of exact results and quantum Monte Carlo data for the entanglement of formation, we show that the ground state of anisotropic two-dimensional S=1/2 antiferromagnets in a uniform field takes the classical-like form of a product state for a particular value and orientation of the field, at which the purely quantum correlations due to entanglement disappear. Analytical expressions for the energy and the form of such states are given, and a novel type of exactly solvable two-dimensional quantum models is therefore singled out. Moreover, we show that the field-induced quantum phase transition present in the models is unambiguously characterized by a cusp minimum in the pairwise-to-global entanglement ratio R, marking the quantum-critical enhancement of multipartite entanglement.
authors.affiliation: Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 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