2018/06/30 by Tim Lappe, Anna Posazhennikova, Johann Kroha
Physics and Astronomy · #Bose–Einstein condensate #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Physics #Quantum electrodynamics #Quantum many-body systems #Strong Light-Matter Interactions #cond-mat.quant-gas #quant-ph
paper · pdf · doi:10.1103/physreva.98.023626
published as Phys. Rev. A 98, 023626 (2018) · Phys Rev. A, published version, display of some figures improved, references corrected. 12 pages, 7 figures
arxiv created 2018/08/10 · openalex publication_date 2018/08/24 · arxiv updated 2018/11/06 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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 \stackrel\ifmmode \else \~\fi\ensuremathωJ is in resonance with the effective fluctuation energy \stackrel\ifmmode \else \~\fi\ensuremathεm, where both \stackrel\ifmmode \else \~\fi\ensuremathωJ and \stackrel\ifmmode \else \~\fi\ensuremathεm 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.