Nontrivial entanglement passively mediated by a quenched magnetic impurity

Abstract

We investigate the entanglement properties of a Kondo system undergoing a transition to a state with a quenched magnetic impurity, using the density matrix renormalization group method. We focus on a two-channel spin-1 Kondo impurity with single-ion anisotropy, where a quantum phase transition occurs between two topologically distinct local Fermi liquids. In the fully screened Kondo phase, realized at lower anisotropies, the entangled region surrounding the magnetic impurity mimics the Kondo screening cloud, although its length does not follow the conventional behavior. In contrast, beyond the transition, the system enters a non-Landau Fermi liquid phase with a markedly different entanglement structure: As the impurity is quenched and disentangled from the rest of the system due to the breakdown of the Kondo effect, the two conduction channels—coupled only through the impurity—develop a significant degree of entanglement with one another. Our findings demonstrate that a quenched magnetic impurity can passively and efficiently mediate entanglement between spatially separated conduction bands.