Signatures of many-body localisation in the dynamics of two-sites entanglement

We are able to detect clear signatures of dephasing - a distinct trait of Many-Body Localisation (MBL) - via the dynamics of two-sites entanglement, quantified through the concurrence. Using the protocol implemented in \[Science {\bf 349}, 842 (2015)\] we show that - in the MBL phase - the average two-site entanglement decays in time as a power law, while in the Anderson localised phase it tends to a plateau. The exponent of the power law is not universal and shows a clear dependence on the strength of the interaction. This behaviour is also qualitatively different in the ergodic phase where the two-site entanglement decays exponentially. All the results are obtained by means of time-dependent density matrix renormalisation group simulations; they are corroborated by analytical calculations on an effective model. Two-site entanglement has been already measured in cold atoms: Our analysis paves the way for the first direct experimental test of many-body dephasing in the MBL phase.