Long-Range Entanglement near a Kondo-Destruction Quantum Critical Point

The numerical renormalization group is used to study quantum entanglement in the Kondo impurity model with a density of states ρ(| |r (0<r<12) that vanishes at the Fermi energy =0. This nonintegrable model features a Kondo-destruction quantum critical point (QCP) separating a partially screened phase from a local-moment phase. The impurity contribution Seimp to the entanglement entropy between a region of radius R around the magnetic impurity and the rest of the system reveals a length scale R∗ that distinguishes a region RR∗ of strong critical entanglement from one RR∗ of weak entanglement. Within each phase, Seimp is a universal function of R/R∗ with a power-law decay for R/R∗1. The entanglement length R∗ diverges on approach to the interacting QCP, showing that the critical Kondo screening cloud subsumes the entire system as the impurity becomes maximally entangled with the conduction band. This work has implications for entanglement calculations in other models and for the nature of heavy-fermion quantum criticality.