Dynamical mean-field theory for Rényi entanglement entropy and mutual information in the Hubbard model

Quantum entanglement, lacking any classical counterpart, provides a fundamental new route to characterize the quantum nature of many-body states. In this work, we discuss an implementation of a new path integral method [Phys. Rev. Res. 2, 033505 (2020)] for fermions to compute entanglement for extended subsystems in the Hubbard model within dynamical mean-field theory (DMFT) in one and two dimensions. The new path integral formulation measures entanglement by applying a "kick" to the underlying interacting fermions. We show that the Rényi entanglement entropy can be extracted efficiently within the DMFT framework by integrating over the strength of the kick term. Using this method, we compute the second Rényi entropy as a function of subsystem size for metallic and Mott insulating phases of the Hubbard model. We explore the thermal entropy to entanglement crossover in the subsystem Rényi entropy in the correlated metallic phase. We show that the subsystem-size scaling of the second Rényi entropy is well described by the crossover formula which interpolates between the volume-law thermal Rényi entropy and the universal boundary-law Rényi entanglement entropy with logarithmic violation, as predicted by conformal field theory. We also study the mutual information across the Mott metal-insulator transition.