Stuttgart 2012 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 22: Quantengase: Wechselwirkungseffekte 1

Q 22.1: Group Report

Tuesday, March 13, 2012, 10:30–11:00, V7.03

Dipolar Bose-Einstein Condensates with Weak Disorder — •Axel Pelster — Hanse-Wissenschaftskolleg, Delmenhorst, Germany

Recent progress nourishes the prospects of future experiments which investigate Bose-Einstein condensates (BECs) with a strong anisotropic and long-range dipole-dipole interaction. Against this background we solve semiclassicaly the Bogoliubov-de Gennes theory for harmonically trapped dipolar BECs which is justified in the thermodynamic limit [1]. In this way we predict for various static and dynamic observables quantum fluctuations, which go beyond the so far experimentally established mean-field theory.
Furthermore, we report on recent progress in understanding the properties of ultracold bosonic atoms in potentials with quenched disorder [2]. This notoriously difficult dirty boson problem is experimentally relevant for the miniaturization of BECs on chips and can also be studied by tailoring disorder potentials via laser speckle fields. Theoretically it is intriguing because of the competition of localization and interaction as well as of disorder and superfluidity.
Finally, we combine both previous topics and consider the impact of weak disorder upon a polarized homogeneous dipolar BEC. We find that both disorder [3] and thermal fluctuations lead to anisotropic superfluidity which can only be described by a corresponding extension of the standard hydrodynamic Landau-Khalatnikov (LK) theory. A linearization of the modified LK equations yields for first and second sound a characteristic direction dependence which should be detectable with Bragg spectroscopy.
[1] A.R.P. Lima and A. Pelster, Phys. Rev. A 84, 041604(R) (2011) and arXiv:1111.0900.
[2] R. Graham and A. Pelster, Int. J. Bif. Chaos 19, 2745 (2009).
[3] C. Krumnow and A. Pelster, Phys. Rev. A 84, 021608(R) (2011).