Hannover 2010 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 55: Poster II

Q 55.14: Poster

Donnerstag, 11. März 2010, 16:00–19:00, Lichthof

Equilibrium and out-of-equilibrium properties of ultracold fermions in optical lattices — •Robert Jördens, Leticia Tarruell, Daniel Greif, Thomas Uehlinger, Niels Strohmaier, Henning Moritz, and Tilman Esslinger — Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland

We present the results of a combined experimental and theoretical study of repulsively interacting ⁴⁰K atoms in the Hubbard model. Accurate measurements of the double occupancy provide direct access to the system’s properties both in equilibrium and in the linear response regime. By calibrating the equilibrium double occupancy against theoretical models over a wide range of parameters we develop a reliable measure for the entropy in the lattice. We demonstrate the applicability of both high-temperature series and dynamical mean field theory to obtain quantitative agreement with the experimental data.

Additionally, we perform weak lattice modulation and monitor the increase of doublons with time. The observations are well captured by linear response theory and are sensitive to local spin ordering, which can be used to detect anti-ferromagnetic states. For long modulation times the system is driven into a far-from-equilibrium state with many additional doublons. We show that the dominant decay mechanism is a high-order scattering process and the doublon lifetime depends exponentially on the ratio of onsite interaction to tunneling energy.