Witnessing nonequilibrium entanglement dynamics in a strongly correlated fermionic chain*

Many-body entanglement has a profound impact on the macroscopic behavior of condensed matter quantum phases. In equilibrium, multipartite entanglement has been diagnosed from response functions through the use of entanglement witnesses together with operator-specific quantum bounds. Here, we investigate the applicability of this approach for detecting entangled states in quantum systems driven out of equilibrium. We use a multipartite entanglement witness, the quantum Fisher information, to study the dynamics of a paradigmatic fermionic chain undergoing a time-dependent ramp of the nearest-neighbor Coulomb interaction. We demonstrate that the quantum Fisher information is able to certify multipartite entanglement both near and far from equilibrium and is robust against decoherence. Our results bear implications for characterizing light-driven states without equilibrium analogues and identifying the role of quantum coherence in the absence of well-defined order parameters.