Hannover 2016 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 17: Quantum Gases: Bosons I

Q 17.1: Group Report

Tuesday, March 1, 2016, 11:00–11:30, e001

Rosensweig instability and solitary waves in a dipolar Bose-Einstein condensate — •Matthias Wenzel, Holger Kadau, Matthias Schmitt, Igor Ferrier-Barbut, and Tilman Pfau — 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany

Ferrofluids show unusual hydrodynamic effects due to the magnetic nature of their constituents. For increasing magnetization a classical ferrofluid undergoes a Rosensweig instability and creates self-organized ordered surface structures or droplet crystals.
In the experiment we observe a similar behavior in a sample of ultra-cold dysprosium atoms, a quantum ferrofluid. By controlling the short-range interaction with a Feshbach resonance we can induce a finite-wavelength instability due to the dipolar interaction.
Subsequently, we observe the spontaneous transition from an unstructured superfluid to an ordered arrangement of droplets by in situ imaging. These patterns are surprisingly long-lived and show hysteretic behavior. When transferring the sample to a waveguide we observe mutually interacting solitary waves. Time-of-flight measurements allow us to show the existence of an equilibrium between dipolar attraction and short-range repulsion. In addition we observe interference between droplets.
In conclusion, our system shows both superfluidity and translational symmetry breaking. This novel state of matter is thus a possible candidate for a supersolid ground state.