Heidelberg 2015 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 5: Quantum Gases: Bosons I

Q 5.3: Talk

Monday, March 23, 2015, 12:00–12:15, P/H2

Experimental realization of a Bose-Hubbard model with long-range interactions — •Renate Landig, Lorenz Hruby, Nishant Dogra, Rafael Mottl, Tobias Donner, and Tilman Esslinger — Institute for Quantum Electronics, ETH Zürich, Switzerland

The combination of strongly correlated systems with long-range interactions gives rise to rich physics with a variety of complex phases, which are often very little understood. Realizing such systems with ultracold atoms offers the perspective to address open questions in a highly controlled way. For example, in the case of cavity-mediated long-range interactions, the competition with short-range interactions is expected to lead to a supersolid, a charge density wave as well as a checkerboard Mott insulating phase.

In our experiment, we couple the external degree of freedom of a quantum gas of Rb-87 to an optical high-finesse cavity. When increasing the cavity-mediated long-range interactions, the quantum gas exhibits a phase transition from a superfluid to a self-organized state with checkerboard density modulation. We measure the dynamic structure factor, which captures the energy and lifetime of elementary excitations, as well as the amount of density fluctuations and correlations via cavity-enhanced inelastic scattering of photons. For strong short-range interactions, achieved by loading the atoms into additional optical lattices, we observe a density-modulated state without coherence, which we associate with a Mott insulating checkerboard phase. We demonstrate first experimental results on the phase diagram of a Bose-Hubbard model with long-range interactions.