1109.4364 (S. Langer et al.)

Expansion velocity of a one-dimensional, two-component Fermi gas during
the sudden expansion in the ballistic regime    [PDF]

S. Langer, M. J. A. Schuetz, I. P. McCulloch, U. Schollwock, F. Heidrich-Meisner

We show that in the sudden expansion of a spin-balanced two-component Fermi gas into an empty optical lattice induced by releasing particles from a trap, over a wide parameter regime, the radius $R_n$ of the particle cloud grows linearly in time. This allow us to define the expansion velocity $V_{ex}$ from $R_n=V_{ex}t$. The goal of this work is to clarify the dependence of the expansion velocity on the initial conditions which we establish from time-dependent density matrix renormalization group simulations, both for a box trap and a harmonic trap. As a prominent result, the presence of a Mott-insulating region leaves clear fingerprints in the expansion velocity. Our predictions can be verified in experiments with ultra-cold atoms.

View original: http://arxiv.org/abs/1109.4364