ISBN 9783843931809

978-3-8439-3180-9, Reihe Physik

Matthias Schmitt
A Self-bound Dilute Quantum Liquid of Dysprosium Atoms

112 Seiten, Dissertation Universität Stuttgart (2017), Softcover, A5

Zusammenfassung / Abstract

Self-bound many-body systems are formed through a balance of attractive and repulsive forces and these systems occur in many physical scenarios. For example liquid droplets are formed by a balance of the mutual attractive and repulsive forces that derive from different components of the inter-particle potential. However, the creation of self-bound ensembles of ultracold atoms has not been possible up to now because they require forces other than the usual short-range contact interaction, which is either attractive or repulsive but never both. In contrast to purely contact interacting gases, a dipolar Bose-Einstein condensate adds the dipolar interaction that itself can be attractive or repulsive. The recent observation that such a dipolar Bose-Einstein condensate restabilizes to quantum droplets after an initial collapse paved the way for a new research direction that goes beyond the standard mean-field approach. In this thesis, we report on the observation that these droplets can become self-bound in a trap-free levitation field and that they exhibit similar properties as a quantum liquid. We observe the existence of a critical number of atoms for the dilute magnetic quantum liquid, below which it evaporates into an expanding gas. Consequently, we observe an interaction-driven phase transition around this critical atom number between a self-bound liquid and a gas in the quantum degenerate regime.