EPL (Europhysics Letters)

EPL, 82 (2008) 30004
DOI: 10.1209/0295-5075/82/30004

Self-trapping of impurities in Bose-Einstein condensates: Strong attractive and repulsive coupling

M. Bruderer¹, W. Bao² and D. Jaksch¹

¹ Clarendon Laboratory, University of Oxford - Parks Road, Oxford OX1 3PU, UK, EU
² Department of Mathematics and Center for Computational Science and Engineering, National University of Singapore - 117543, Singapore

m.bruderer@physics.ox.ac.uk

received 25 January 2008; accepted in final form 9 March 2008; published May 2008
published online 16 April 2008

Abstract
We study the interaction-induced localization $\hbox$ the so-called self-trapping $\hbox$ of a neutral impurity atom immersed in a homogeneous Bose-Einstein condensate (BEC). Based on a Hartree description of the BEC we show that $\hbox$ unlike repulsive impurities $\hbox$ attractive impurities have a singular ground state in 3d and shrink to a point-like state in 2d as the coupling approaches a critical value $\beta^{\star}$ . Moreover, we find that the density of the BEC increases markedly in the vicinity of attractive impurities in 1d and 2d, which strongly enhances inelastic collisions between atoms in the BEC. These collisions result in a loss of BEC atoms and possibly of the localized impurity itself.

PACS
03.75.-b - Matter waves.
67.85.-d - Ultracold gases, trapped gases.
67.85.Bc - Static properties of condensates.

© EPLA 2008