Negative tripartite mutual information after quantum quenches in integrable systems

The tripartite information (TMI) has emerged as a tool to sieve quantum correlations in quantum many-body systems. A negative TMI is interpreted as evidence for quantum information delocalization in chaotic systems. Here, the authors show that a negative TMI can appear in out-of-equilibrium free-fermion models, and it is linked to the presence of entangled multiplets of excitations. Negative TMI signals a weakening of the relationship between entanglement and thermodynamics, which can be understood in a generalized quasiparticle picture framework.