Rostock 2019 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 9: Ultra-cold atoms and molecules II (joint session A/MO/Q)

Q 9.3: Talk

Monday, March 11, 2019, 14:30–14:45, S HS 1 Physik

Anisotropic Superfluid Behavior of a Dipolar Bose-Einstein Condensate — •Jan-Niklas Schmidt, Matthias Wenzel, Fabian Böttcher, Tim Langen, Igor Ferrier-Barbut, and Tilman Pfau — 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology IQST, Universität Stuttgart

Superfluidity still represents a hallmark of quantum physics. Its discovery in liquid helium was one of the first proofs for the influence of quantum effects at the macroscopic scale. The famous Landau criterion connects the maximal velocity for fritionless flow, mainly a transport property of such a superfluid, and its spectrum of elementary excitations. Later various transport measurements could show that also a Bose-Einstein condensate (BEC) features these properties, where the breakdown of superfluid flow can be probed by moving a microscopic impurity through the condensate. In case of a BEC of atoms with strong magnetic dipole-dipole interaction the breakdown of superfluid flow becomes directional, which directly can be seen as a probe of the anisotropic dipolar excitation spectrum.

During this talk we present transport measurements using a dipolar BEC of highly magnetic ¹⁶²Dy atoms, where we move an attractive laser beam through the condensate and observe an anisotropic superfluid flow. The critical velocity and the above starting heating rate is in excellent agreement with fully numerical simulations of the extended Gross-Pitaevskii equations that mimic our particular system.