Correlations between particles can lead to subtle and sometimes counterintuitive phenomena. We analyze one such case, occurring during the sudden expansion of fermions in a lattice when the initial state has a strong admixture of double occupancies.
We promote the notion of quantum distillation: during the expansion, and in the presence of strongly repulsive interactions, doublons group together, forming a nearly ideal band insulator, which is metastable with a low entropy. We propose that this effect could be used for cooling purposes in experiments with two-component Fermi gases.
We study the sudden expansion of strongly correlated fermions in a one-dimensional lattice, utilizing the time-dependent density-matrix renormalization group method. Our focus is on the behavior of experimental observables such as the density, the mo
mentum distribution function, and the density and spin structure factors. As our main result, we show that correlations in the transient regime can be accurately described by equilibrium reference systems. In addition, we find that the expansion from a Mott insulator produces distinctive peaks in the momentum distribution function at |k| ~ pi/2, accompanied by the onset of power-law correlations.
