Dresden 2011 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 57: Poster 3: Quantengase, Ultrakalte Atome, Ultrakalte Moleküle, Materiewellen Optik, Präzisionsmessungen, Metrologie
Q 57.43: Poster
Donnerstag, 17. März 2011, 16:30–19:30, P1
The Dicke quantum phase transition in an optical cavity QED system — •Rafael Mottl1, Kristian Baumann1, Ferdinand Brennecke1, Tobias Donner1, Christine Guerlin2, and Tilman Esslinger1 — 1Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland — 2Thales Research and Technology, 91767 Palaiseau Cedex, France
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. We have achieved its first experimental realization in an open system in which a Bose-Einstein condensate is loaded into an optical high-finesse cavity. The superfluid atoms collectively couple a far-detuned pump field to the empty cavity mode. Above a critical pump power the atoms self-organize into an emergent checkerboard pattern which shows supersolid character. The boundary of this novel phase was mapped out and coincides with its theoretical description by the Dicke model. Investigating the excitation spectrum below threshold by Bragg spectroscopy, we could identify a vanishing energy gap when approaching the critical point - a precursor of the quantum phase transition.