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A: Fachverband Atomphysik
A 26: Posters: BECs, ultracold gases and plasmas
A 26.17: Poster
Thursday, March 13, 2008, 16:30–18:30, Poster C3
A frozen Rydberg gas as a model system for quantum critical phenomena — •Peter Kollmann1, Björn Butscher1, Hendrik Weimer2, Ulrich Raitzsch1, Rolf Heidemann1, Vera Bendkowsky1, Robert Löw1, Hans Peter Büchler2, and Tilman Pfau1 — 15. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart — 2Institut für Theoretische Physik III, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart
We present our recent experimental results on Rydberg excitation of magnetically trapped Rubidium atoms.
In a thermal cloud of a few µK we observe coherent, collective and strongly blocked excitation induced by the van der Waals interaction among the Rydberg atoms [1]. The observed scaling behaviour can be well understood in the framework of critical phenomenona. The reversibility of the excitation dynamics was measured with an echo type technique [2]. With this experiments we prove the coherence of the excitation and gain insight into the dephasing due to interactions. We further observed a signature of the phase transition to a Bose-Einstein condensate in the fraction of excited Rydberg atoms when cooling the thermal cloud below Tc. The main features of the experimental data are reproduced by a simulation using a superatom model [3].
[1] R. Heidemann et al., Phys. Rev. Lett. 99, 163601 (2007)
[2] U. Raitzsch et al., arXive: quant-phys 0706.2639 (2007)
[3] R. Heidemann et al., arXive: cond-mat 0710.5622 (2007)