Quasilocal entanglement across the Mott-Hubbard transition

The possibility to directly measure, in a cold-atom quantum simulator, the entanglement and mutual information between a site and its environment opens new perspectives on the characterization of the Mott-Hubbard metal-insulator transition, in the framework of quantum information theory. In this work we provide an alternative view of the Mott transition in the two-dimensional Hubbard model in terms of suitably defined quasilocal measures of entanglement and correlation between two spatially separated electronic orbitals, with no contribution from their environment. A space-resolved analysis of Cluster Dynamical Mean-Field Theory results elucidates the prominent role of the nearest-neighbor entanglement in probing Mott localization: both its lower and upper bounds sharply increase at the metal-insulator transition. The two-site entanglement beyond nearest neighbors is shown to be quickly damped as the inter-site distance is increased. These results ultimately resolve a conundrum of previous analyses based on the single-site entanglement, which has been found to monotonically decrease when the interaction is increased. The quasilocal two-site entanglement recovers instead the distinctive character of Mott insulators as strongly correlated quantum states, demonstrating the central role of this marker in the two-dimensional Hubbard model.