Anisotropic scattering of Bogoliubov excitationsC. Gaul and C. A. Müller
Universität Bayreuth - 95440 Bayreuth, Germany, EU
received 26 March 2008; accepted in final form 22 May 2008; published July 2008
published online 18 June 2008
We consider elementary excitations of an interacting Bose-Einstein condensate in the mean-field framework. As a building block for understanding the dynamics of systems comprising interaction and disorder, we study the scattering of Bogoliubov excitations by a single external impurity potential. A numerical integration of the Gross-Pitaevskii equation shows that the single-scattering amplitude has a marked angular anisotropy. By a saddle point expansion of the hydrodynamic mean-field energy functional, we derive the relevant scattering amplitude including the crossover from sound-like to particle-like excitations. The very different scattering properties of these limiting cases are smoothly connected by an angular envelope function with a well-defined node of vanishing scattering amplitude. We find that the overall scattering is most efficient at the crossover from phonon-like to particle-like Bogoliubov excitations.
03.75.Kk - Dynamic properties of condensates; collective and hydrodynamic excitations, superfluid flow.
05.60.Gg - Quantum transport.
67.10.Jn - Transport properties and hydrodynamics.
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