Darmstadt 2008 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 44: Quanteneffekte (Interferenz / Sonstige)

Q 44.6: Talk

Thursday, March 13, 2008, 15:15–15:30, 2D

Thermal equilibrium of coupled atom-light states in an ultrahigh pressure buffer gas cell — •Ulrich Vogl, Johannes Nipper, and Martin Weitz — Institut für Angewandte Physik, Wegelerstraße 8, 53115 Bonn

Thermal equilibrium is a prerequisite for most known phase transitions, as Bose-Einstein condensation of dilute atomic gases or many solid state physics concepts. Recently, phase transitions of coupled particle-light degrees of freedom have been investigated in the framework of polariton quasiparticle condensation, and exciton polariton systems gave compelling evidence for a condensation. However, the short polariton lifetimes of around a ps arose questions whether the system is fully thermalized. We investigate the statistical distribution of coupled atom-light excitations in an atomic rubidium gas cell subject to 500 bar buffer gas pressure. The large collisional broadening of this system interpolates between usual atomic physics gas phase and solid/liquid phase conditions. An observed intensity-dependent blue asymmetry of spectra is interpreted as evidence for the approaching of thermal equilibrium of dressed atom-light states.