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A: Fachverband Atomphysik

A 5: Ultra-cold atoms and molecules II (joint session A/MO/Q)

A 5.4: Vortrag

Montag, 11. März 2019, 14:45–15:00, S HS 1 Physik

Dipolar quantum droplets — •Fabian Böttcher, Jan-Niklas Schmidt, Matthias Wenzel, Julian Kluge, Viraatt Sai, Jens Hertkorn, Tim Langen, Arup Bhowmick, Mingyang Guo, and Tilman Pfau — 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology IQST, Universität Stuttgart

The interplay of the short-range and isotropic contact interaction and the long-range and anisotropic dipolar interaction, allows for many interesting phenomena. In the case of the interactions competing with each other the mean-field contribution can get very small so that beyond mean-field effects start to play an important role and can actually stabilize an otherwise collapsing system. In our experiment with dysprosium atoms we observed a phase-transition between a gas and a liquid, characterized by the formation of self-bound droplets. These droplets show a saturation of the peak density with higher number of atoms like other liquids, even though they are 100 million times less dense than liquid helium droplets. The self-bound character of them opens up the mew perspective of a truly isolated quantum system.

With our experiment we can study a single self-bound droplet and measure the critical atom number for the phase transition between liquid droplet and expanding gas for more than an order of magnitude. For a single droplet we can also observe its anisotropic density distribution in-situ, as well as study the collective excitations. Furthermore the tendency of the system to form self-organized structures opens the possibility to reach a supersolid ground state.