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Q: Fachverband Quantenoptik und Photonik

Q 55: Poster II

Q 55.5: Poster

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

The Dicke Model Quantum Phase Transition in a Driven Condensate-Cavity System — •Ferdinand Brennecke, Kristian Baumann, Christine Guerlin, Silvan Leinss, Rafael Mottl, and Tilman Esslinger — Quantum Optics Group, ETH Zurich, Switzerland

The Dicke Model describes the collective interaction between an ensemble of two-level atoms and a single electromagnetic field mode, and remains a fundamental theme in quantum optics. In the thermodynamic limit this system was predicted to undergo a quantum phase transition from a normal to a superradiant phase. Here we present an experimental open-system realization of the Dicke model using a Bose-Einstein condensate coupled to a high-finesse optical cavity. The superfluid atoms collectively couple a far-detuned pump field to an empty cavity mode. Above a critical pump power the atoms self-organize into an emergent checkerboard pattern. When entering this self-organized phase, the gas initially maintains phase coherence and can thus be regarded as a supersolid. Over a wide range of parameters, the boundary of this novel quantum phase is mapped out and compared to a theoretical model. This work opens up new aspects of quantum many-body physics with global interactions mediated by the cavity field.