Fluctuation damping of isolated, oscillating Bose-Einstein condensates

Tim Lappe, Anna Posazhennikova, and Johann Kroha
Phys. Rev. A 98, 023626 – Published 24 August 2018

Abstract

Experiments on the nonequilibrium dynamics of an isolated Bose-Einstein condensate (BEC) in a magnetic double-well trap exhibit a puzzling divergence: While some show dissipation-free Josephson oscillations, others find strong damping. Such damping in isolated BECs cannot be understood on the level of the coherent Gross-Pitaevskii dynamics. Using the Keldysh functional-integral formalism, we describe the time-dependent system dynamics by means of a multimode BEC coupled to fluctuations (single-particle excitations) beyond the Gross-Pitaevskii saddle point. We find that the Josephson oscillations excite an excess of fluctuations when the effective Josephson frequency ω̃J is in resonance with the effective fluctuation energy ɛ̃m, where both ω̃J and ɛ̃m are strongly renormalized with respect to their noninteracting values. By evaluating and using the model parameters for the respective experiments, we describe quantitatively the presence or absence of damping.

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  • Received 1 June 2018

DOI:https://doi.org/10.1103/PhysRevA.98.023626

©2018 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Tim Lappe1,*, Anna Posazhennikova2,†, and Johann Kroha1,3,‡

  • 1Physikalisches Institut and Bethe Center for Theoretical Physics, Universität Bonn, Nussallee 12, 53115 Bonn, Germany
  • 2Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
  • 3Center for Correlated Matter, Zhejiang University, Hangzhou, Zhejiang 310058, China

  • *lappet@th.physik.uni-bonn.de
  • anna.posazhennikova@rhul.ac.uk
  • kroha@th.physik.uni-bonn.de

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Issue

Vol. 98, Iss. 2 — August 2018

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