Fabian Heidrich-Meisner
LMU Munich

"Sudden expansion of interacting fermions in one-dimensional optical lattices"

Experiments with ultracold atomic gases loaded into optical lattices offer
unique possibilities to study the non-equilibrium dynamics of strongly
interacting many-body systems. Substantial work has been devoted to
interaction quenches, with a focus on questions such as relaxation,
thermalization, or the time-evolution of correlations. Quantum quenches
of the confining potential give rise to an expansion of the particle cloud
and thus finite particle currents (see e.g., [1]). In this talk, I will
discuss this set-up for the case of fermions described by the Hubbard model.
First, I will present time-dependent DMRG results for the time-evolution of
density profiles and I will show that for sufficiently small initial
densities, the cloud's radius grows linearly in time, i.e., R=V t. This
allows us to interpret V as the expansion velocity and we have fully clarified
its dependence on initial conditions such as density and interaction strength.
We argue that a measurement of this observable can give valuable information
on the initial state, in particular, the presence of a Mott insulator.
Second, I will demonstrate that for large initial particle densities,
metastable states can emerge in the transient dynamics due to the presence
of doublons, which can be exploited to engineer low-entropy states [3].
Finally, I will discuss the time-evolution of correlation momentum distribution
functions of an attractively interacting gas with a finite spin imbalance [4],
relevant for potential realizations of the Fulde-Ferrell-Larkin-Ovchinnikov state
in experiments with ultracold atoms.

[1] Schneider et al. Nature Phys. 8, 213 (2012)
[2] Langer et al., Phys. Rev. A 85, 043618 (2012)
[3] Heidrich-Meisner et al., PRA 80, 041603(R) (2009)
[4] Bolech, Heidrich-Meisner, Langer, McCulloch, Orso, Rigol, Phys. Rev. Lett.

in press, arXiv:1206.2019.