TY  - GEN
Y1  - 2020///
ID  - heidok28820
CY  - Heidelberg
N2  - The Bose polaron problem is concerned with an impurity particle moving through a Bose-Einstein condensate, which is an instance of the general concept of a particle in medium.
This dissertation investigates the theory of the Bose polaron with a focus on the region of strong coupling between impurity and condensate that marks the transition between attractive and repulsive scattering processes as a scattering resonance is crossed.
We use an analytical study of a heavy impurity in an ideal condensate to obtain detailed insights on the emergence of many-body physics from two-body physics and derive the exact solution of the time evolution.
The interacting Bose gas is treated by the widely-adopted Bogoliubov method, which results in a theory beyond the classical Fröhlich description of polarons.
At strong coupling, the Bogoliubov description is found to be no longer applicable and a new theory for strongly deformed condensates is derived in the form of a non-local extension of Gross-Pitaevskii theory.
We find that the impurity-boson bound state that exists for repulsive coupling is responsible for long-lived coherent oscillations in a number of observables, such as the number of bosons attracted by the impurity, Tan's contact and the density profile of the condensate around the impurity.
The latter exhibits a remarkable depletion halo, which periodically reaches zero density at a certain distance to the impurity.
Polaron trajectories show that the impurity eventually moves like a free quasi-particle with enhanced effective mass for attractive coupling and present velocity oscillations on the repulsive side, leading to stop-and-go motion.
Close to the in-medium resonance, a dynamical transition from a repulsive to an attractive polaron is observed.
AV  - public
TI  - Dynamics of a Strongly Interacting Impurity in a Bose-Einstein Condensate
A1  - Drescher, Moritz
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/28820/
ER  -