Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 29: Other Low Temperature Topics: Cold Atomic Gases

TT 29.2: Vortrag

Dienstag, 21. März 2017, 12:15–12:30, HSZ 201

Quasiparticle-induced Damping of BEC Oscillations in Double-well Potentials — •Tim Lappe¹, Anna Posazhennikova², and Johann Kroha¹ — ¹Physikalisches Institut, Universität Bonn — ²Department of Physics, Royal Holloway, University of London

An interacting Bose-Einstein condensate (BEC) in a double-well trap with initial population imbalance, z₀, can perform Josephson oscillations or be in a self-trapped regime, depending on the value of z₀. Experimentally, both strongly damped [1] and undamped Josephson oscillations [2] have been observed, a discrepancy that has remained controversial because the source of the damping in [1] could not be clearly identified. A known mechanism for damping in such systems is via inelastic collisions of quasiparticles (QPs) [3]. However, in order to compare with real experiments one needs to incorporate the realistic energy spectrum of the potential, temperature effects and condensate contributions to the higher excited levels of the trap. In view of the necessary changes we solve the full non-separable potential of [2] exactly and incorporate all fluctuation effects within the full second order (in the couplings) approximation, thus demonstrating the possibility of QP excitations in the system. By taking into account QP collisions, we can reproduce the damped oscillations.

[1] LeBlanc et. al., Phys. Rev. Lett. 106, 025302 (2011).
[2] Albiez et. al., Phys. Rev. Lett. 95, 010402 (2005).
[3] A. Posazhennikova, M.Trujillo-Martinez, J. Kroha, Phys. Rev. Lett. 116, 225304 (2016).