Freiburg 2024 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 3: Bosonic Quantum Gases I (joint session Q/A)

Q 3.7: Talk

Monday, March 11, 2024, 12:30–12:45, Aula

Dynamics of polaron formation in weakly interacting 1D Bose gases — •Martin Will and Michael Fleischhauer — University of Kaiserslautern-Landau

We discuss the dynamics of the formation of a Bose polaron when an impurity is injected into a weakly interacting one-dimensional Bose condensate. While for small impurity-boson couplings, this process can be described within the Froehlich model as emission, and binding of Bogoliubov phonons, this is no longer adequate if the coupling becomes strong. To treat this regime, we consider a mean-field approach beyond the Froehlich model which accounts for the backaction to the condensate, complemented with Truncated Wigner simulations to include quantum fluctuation. For the stationary polaron we find a periodic energy-momentum relation and non-monotonous relation between impurity velocity and polaron momentum including regions of negative impurity velocity. Consequently, the impurity undergoes Bloch oscillations when subject to a constant force. Studying the polaron formation after turning on the impurity-boson coupling (i) quasi-adiabatically and (ii) in a sudden quench, we find a rich scenario of dynamical regimes. Due to the build-up of an effective mass, the impurity is slowed down even if its initial velocity is below the Landau critical value. For larger initial velocities we find deceleration and even backscattering caused by emission of density waves or grey solitons and subsequent formation of stationary polaron states.

Keywords: Polaron; Formation Dynamics; Impurity; Bosons; Quasiparticle