A paradigmatic example of impurity physics is an electron moving in a crystal lattice, where interactions between the electron and atoms distort the lattice and lead to phononic excitations. This interaction is well described in the quasiparticle framework, where the electron and excitations are considered together as a single particle, which is termed the polaron.

During his PhD studies, Andreas Madsen Morgen studied the Bose polaron using the controlled environment provided by ultracold quantum gases. The polaron was realized by embedding impurities into a Bose-Einstein Condensate (BEC), which allowed for the observation of exotic effects, such as quantum beats between two co-existing polaron states and induced interactions between polarons mediated by the BEC atoms. The results expand upon the current understanding of the Bose polaron and contribute to resolving outstanding theoretical discrepancies.

The PhD study was completed at Department of Physics and Astronomy, Faculty of Natural Sciences, Aarhus University.

This summary was prepared by the PhD student.

Time: Thursday 24 October 2024 at 14:00
Place: Building 1632, room 201, AIAS, The auditorium, Høegh-Guldbergs Gade 6B, Aarhus Universitet, 8000 Aarhus C
Title of PhD thesis: Observation of Quantum Beats and Mediated Interactions – Polarons in Bose-Einstein Condensates
Contact information: Andreas Madsen Morgen, e-mail: anmo@phys.au.dk, tel.: +45 21857614
Members of the assessment committee:
Associate Professor Robert Smith, Department of Physics, Oxford University, England
Professor Jacques Tempere, Department of Physics, University of Antwerp, Belgium
Professor Steen Hannestad (chair), Department of Physics and Astronomy, Aarhus University, Denmark
Main supervisor:
Associate Professor Jan Joachim Arlt, Department of Physics and Astronomy, Aarhus University, Denmark
Language: The PhD dissertation will be defended in English

The defence is public.
The PhD thesis is available for reading at the Graduate School of Natural Sciences/GSNS, Ny Munkegade 120, building 1521, 8000 Aarhus C