Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky
Erscheinungsjahr:
2024
Medientyp:
Text
Schlagworte:
530: Physik
33.23: Quantenphysik
ddc:530:
Beschreibung:
In this thesis, experimental work is presented which enabled few atom counting in a tweezer-based K40 setup, the creation of 3D Bose-Einstein condensates of K39, the achievement of quantum degeneracy in bosonic 2D samples, and of local probing of polaronic physics therein. Starting from an apparatus capable of laser cooling fermionic K40, a novel dual-color magneto-optical trap capable of detecting individual atoms was implemented. This allowed reliable atom number determination with fidelities of 98% for up to five atoms and >85% for up to 17 atoms. Upgrading the setup enabled us to achieve Bose-Einstein-condensation of K39, and by utilizing suitable optical potentials, to create two-dimensional samples in the regime of BKT superfluidity. In both the 2D and 3D gases polaronic physics was then studied by employing radio-frequency pulses to flip a fraction of the atoms into a strongly interacting impurity state. The polaron spectrum was measured in both cases across a Feshbach resonance, allowing us to tune the strength as well as the sign of the bath-impurity interaction. To model the spectral line shapes with good accuracy it was necessary to include excited polaronic states, in contrast to previous work. Taking advantage of our machine's high optical resolution, spatially and temporally resolved impurity dynamics in the BKT-gas was experimentally investigated for the first time. The spatial impurity distribution observed in frequency-resolved measurements exhibits significant differences between attractive and repulsive interactions, supporting the relevance of excited polaron states. For repulsive interactions we observe an outward motion of the impurities and ultimately the expulsion of the impurities from the bath. We can accurately describe this motion when including the predicted friction term for velocities above the speed of sound.