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A: Fachverband Atomphysik

A 4: Quantum gases II (jointly with Q)

A 4.2: Group Report

Monday, March 10, 2008, 17:00–17:30, 1A

Bose-Einstein condensates in presence of defects and disorder. — •Tobias Paul, Mathias Albert, Nicolas Pavloff, and Patricio Leboeuf — Laboratoire de Physique Théorique et Modèles Statistiques, Universite Paris Sud, F-91405 Orsay

Superfluidity and Anderson localization are genuine many-body manifestations of quantum coherence which are nowadays revisited in dilute Bose gases. Recent theoretical results obtained in our group in Orsay are reviewed: First, we study the coherent flow of interacting Bose-condensed atoms in presence of a single defect or an extended disorder potential. We discuss the different regimes of quantum transport induced by a variation of the condensate flow-velocity v: We point out that for v much smaller than the sound velocity c the flow is in general superfluid, whereas beyond a critical velocity the formation of solitons and shockwaves sets on. For v ≫ c, a regime of quasi-dissipationless transport is found. There, for long disorder samples, the system enters an Anderson localized phase.

In a second step, we consider the experimental relevant case where a harmonic trap is superimposed to the defect potential. We obtain a global picture characterizing the dynamical properties of the dipole oscillations where we recover the different regimes of quantum transport introduced in the first part of the talk. We discuss our findings in the context of recent experiments [1,2] and address the question under which circumstances Anderson localization could be observed.

[1] J. E. Lye et al., Phys. Rev. A 75, 061603 (2007)

[2] P. Engels and C. Atherton, Phys. Rev. Lett. 99, 160405 (2007)