Frankfurt 2006 – scientific programme

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A: Atomphysik

A 6: Ultrakalte Atomphysik II: Dynamik mit Bose-Einstein Kondensaten

A 6.1: Invited Talk

Tuesday, March 14, 2006, 14:00–14:30, H6

Interaction-Induced Localization of an Impurity in a Trapped Bose Condensate — •Doerte Blume — Department of Physics and Astronomy, Washington State University, Pullman, WA 99164-2814

The behaviors of weakly interacting Bose gases have been successfully modeled within a mean-field framework. To this end, one replaces the true atom-atom potential by a contact interaction, and solves the resulting many-body Schroedinger equation at the Hartree level. The resulting non-linear single-particle Schroedinger equation, also referred to as Gross-Pitaevskii equation, predicts many behaviors of inhomogeneous Bose gases accurately, including the onset of instability for Bose systems with negative two-body s-wave scattering length for a critical number of particles. Motivated by rapid experimental pogress, we study the ground state properties of a trapped Bose condensate with a neutral impurity. Our self-consistent mean-field treatment provides a first step towards a systematic understanding of impurities in a Bose condensate. We find that the degree of localization of the impurity at the trap center can be controlled by varying the strength of the attractive atom-impurity interactions. As the impurity becomes more strongly localized the peak condensate density, which can be monitored experimentally, grows markedly. For strong enough attraction, the impurity can make the condensate unstable by strongly deforming the atom density in the neighborhood of the impurity. This No-dqcollapseNo-dq can possibly be investigated in bosenova-type experiments. We also discuss a simple variational treatment which reproduces the key features of the self-consistent results. *This work is supported by the NSF.