Berlin 2008 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 15: Controlling Dirty Bosons: Disorder Effects on BECs

DY 15.3: Talk

Tuesday, February 26, 2008, 15:00–15:15, MA 001

Dipole Oscillations of a Bose-Einstein Condensate 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

We study the dipole oscillations of a weakly interacting BEC, confined in a harmonic cigar-shaped trap with a tight transverse confinement but a shallow axial trapping frequency in presence of an external defect or random potential. Our main result is a new, global picture characterizing the dynamical properties of the dipole oscillations, where different regimes of condensate dynamics are observed: For small-amplitude dipole oscillations we demonstrate that the BEC-flow is superfluid and the dipole oscillations are almost undamped, but the external potential induces a small shift of the oscillations frequency. When the center of mass motion reaches a critical velocity the superfluid behavior breaks down and one enters a regime of dissipative dynamics characterized by a strong damping of the dipole oscillations. We show that the onset of this domain is marked by the emergence of gray solitons. For large-amplitude oscillations a regime of quasi-dissipationless transport is found where the creation of elementary excitations is strongly oppressed. We discuss our findings in the context of recent experimental observation [1,2,3] and address the question under which circumstances Anderson localization is of relevance for these systems.

[1] C. Fort et al., Phys. Rev. Lett. 95, 170410 (2005)

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

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