Exploring Symmetry Breaking at the Dicke Quantum Phase Transition
Kristian Baumann, Rafael Mottl, Ferdinand Brennecke, Tilman Esslinger · Physical Review Letters · 2011
We study symmetry breaking at the Dicke quantum phase transition by coupling a motional degree of freedom of a Bose-Einstein condensate to the field of an optical cavity. Using an optical heterodyne detection scheme, we observe symmetry breaking in real time and distinguish the two superradiant phases. We explore the process of symmetry breaking in the presence of a small symmetry-breaking field and study its dependence on the rate at which the critical point is crossed. Coherent switching between the two ordered phases is demonstrated.