Studies of a dipolar quantum gas: Towards Er-K mixture

Jiri Kucera - Balliol College - University of Oxford
2024 - DPhil thesis

In this work we present an overview of the current state of the Oxford erbium-potassium experiment and the scientific discoveries that have been made with it.
Namely, we describe the experimental procedure and techniques that lead to a production of a large (> 200×103) Bose-Einstein condensates of 166Er in a crossed-beam optical dipole trap with atomic transport capabilities using focus-tunable lenses.
We then discuss our measurement of the three-body loss in 166Er between 0 − 4 G.
Our findings reveal new features that display strong temperature dependence, hinting at their higher partial wave character due to the anisotropic dipole-dipole interactions (DDIs) between erbium atoms. We also present a refined model of the three-body loss process which accounts for secondary collisions and excess heating.
The richness of physical phenomena brought about by the long-range DDI is furthermore demonstrated by considering its contribution to the shift in the critical temperature of a dipolar condensate and its depletion as compared to the purely contact interaction case. We present the first experimental measurement of this effect together with an outline of the theoretical model that accounts for our observations.
Lastly, we report on the construction of a 2D+ magneto-optical trap (MOT) for potassium.
We describe the technical details of our optical setup and vacuum assembly as well
as present initial measurements of the 2D MOTs performance as a steady source of cold atoms. Successful implementation of this stage marks a major step towards the realization of the first ultracold Er-K mixture.
We conclude by discussing the short term goals which include construction of a dual
species 3D MOT and inter-species Feshbach resonance measurements, as well as the long term aims of the experiment which revolve around utilizing a novel, quasi-2D potential for studying impurity physics in homogeneous degenerate dipolar gases.