Sudden Expansion of Interacting Fermions in One-Dimensional Optical Lattices

When: Wednesday, September 05, 2012 at 12:00 pm
Where: DA 114
Speaker: Fabian Heidrich-Meisner
Organization: LMU Munich
Sponsor: Physics Seminar

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.  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. We propose that the asymptotic form of the momentum distributions can be related to integrals of motion of this integrable quantum model [4].

[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

Host: Assistant Professor Adrian Feiguin