Rostock 2019 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 27: Quantum gases (Bosons) (joint session A/Q)
A 27.1: Vortrag
Donnerstag, 14. März 2019, 10:30–10:45, S HS 1 Physik
Squeezed field path integral description of second sound in Bose-Einstein condensates — •Mir Heliassudin Ilias Seifie1,2, Vijay Pal Singh1,2,3, and Ludwig Mathey1,2,3 — 1Zentrum für Optische Quantentechnologien, Universität Hamburg, 22761 Hamburg, Germany — 2Institut für Laserphysik, Universität Hamburg, 22761 Hamburg, Germany — 3The Hamburg Center for Ultrafast Imaging, Luruper Chaussee 149, Hamburg 22761, Germany
We propose a generalization of the Feynman path integral using squeezed coherent states by introducing a squeezing parameter into the path integral. As a result the adaptability of the theoretical model to the physical system is enhanced. Therefore, our method can be applied to any analytical and numerical approach that is based on the path integral representation. We apply this approach to the dynamics of Bose-Einstein condensates, which gives an effective low energy description that contains both a coherent field and a squeezing field. We derive the classical trajectory of this action, which constitutes a generalization of the Gross Pitaevskii equation, at linear order. We derive the low energy excitations, which provides a description of second sound in weakly interacting condensates as a squeezing oscillation of the order parameter. This interpretation is also supported by a comparison to a numerical c-field method.