Scaling, Entanglement, and Quantum Phase Transitions

We study the entanglement near a quantum phase transition in a class of exactly solvable one‐dimensional quantum magnets, the anisotropic XY models. The critical behaviour (scaling) is reflected by the derivatives of the bipartite entanglent, quantified by the concurrence. However, we found a profound difference between classical correlation and non‐local quantum correlation: The range of the concurrence is found to behave in a non‐universal way, being extremely short‐ranged for the Ising model. This range tends to infinity towards the isotropic XY model.