Interactions in a Quantum Gas of Dysprosium Atoms

Thomas Maier, Prof. Dr. Tilman, Prof. Dr. Harald Giessen, Prof. Dr. Günter Wunner

Abstract

The subject of this thesis is the creation of a dipolar quantum gas of dysprosium atoms as well as the investigation of its two-body interactions. For this purpose we setup a new experimental apparatus which allows us to study dipolar many-body systems with ultra-cold bosonic 164Dy, 162Dy as well as fermionic 161Dy atoms. In this work I present our developed cooling and trapping scheme to create a cold sample of dysprosium atoms based on a magneto-optical trap operating at the 626 nm transition and forced evaporative cooling in a crossed optical dipole trap. With our methods we can create Bose-Einstein condensates with N ≈ 25 × 103 (N ≈ 30 × 103) atoms of the 164Dy (162Dy) isotope, respectively. In addition, degenerate Fermi gases with N ≈ 10 × 103 and T/TF ≈ 0.5 can be realized. By comparing the experimentally obtained data with the prediction of theoretical calculations we show that for both bosonic isotopes the dipole-dipole interaction dominates the two-body interaction energy. Furthermore, we observe the effects of the complex atomic structure of dysprosium as a dense and correlated distribution of narrow Feshbach resonances. Despite many narrow resonances we also observe broad resonances which are caused by universal s-wave halo states. These resonances offer the possibility to tune the two-body interactions in dysprosium in a controlled way.