The expansion of strongly interacting fermions after the release from a trap

Both the recent experimental progress in cold atom gas realizations and developments in computational techniques has fueled interest in nonequilibrium properties of strongly correlated systems. Here we study the expansion of fermions in a one-dimensional lattice after released from a trap. Using the time-dependent density matrix renormalization group method, we analyze properties of the one-particle density matrix as well as the evolution of spin and density correlations. A comparison of particles escaping from a metallic region as compared to a Mott-insulating one shows that some memory on the initial state is preserved during the expansion. We further address the question to what extent the correlations measured during the expansion and thus in a non-equilibrium situation resemble those of appropriately chosen reference systems in equilibrium.