title: Cs-133 atoms in a Li-6 Fermi sea for exploring polaron physics in the heavy impurity limit
creator: Lippi, Eleonora
subject: ddc-530
subject: 530 Physics
description: The thesis deals with the experimental study of dilute ultracold gases of Cs-133 atoms mixed with a degenerate Fermi Sea of Li-6 atoms. It focuses on the problem of the coupling of an impurity to a surrounding quantum bath, which can be described as a quasi-particle known as polaron.   The large mass imbalance between the impurity (Cs) and the bath (Li) leads to unique many-body phenomena, but also poses significant experimental challenges for mixing the two species at ultracold temperature where Li is quantum degenerate. In this work, we realize a mixture of a degenerate Li Fermi Sea and a dilute thermal Cs gas by adopting a bichromatic trapping approach and implementing a tightly confining and movable single beam trap for Li at the Cs tune-out wavelength. This allows the sequential preparation of the Li Fermi Sea, which can be overlapped with Cs atoms in a controlled manner, compensating for the differential gravitational sag between the two species.    To probe the Fermi-polaron scenario, an optical spectroscopic method based on two-photon Raman transitions between the two lowest Zeeman states of Cs is implemented. Guided by theoretical predictions of the polaron spectral function, ejection spectroscopy on Cs impurities is performed to map the polaron energy spectrum as a function of interaction strength near a Li-Cs Feshbach resonance at 890 G, which provides high tunability of the interspecies interactions. Limitations to this kind of experiments and strategies to overcome them are discussed, laying the groundwork for exploring polaron physics with heavy mass impurities.
date: 2024
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserver/35527/1/Dissertation_EleonoraLippi.pdf
identifier: DOI:10.11588/heidok.00035527
identifier: urn:nbn:de:bsz:16-heidok-355274
identifier:   Lippi, Eleonora  (2024) Cs-133 atoms in a Li-6 Fermi sea for exploring polaron physics in the heavy impurity limit.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/35527/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng