Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                

Anisotropic Superfluid Behavior of a Dipolar Bose-Einstein Condensate

Matthias Wenzel, Fabian Böttcher, Jan-Niklas Schmidt, Michael Eisenmann, Tim Langen, Tilman Pfau, and Igor Ferrier-Barbut
Phys. Rev. Lett. 121, 030401 – Published 17 July 2018
PDFHTMLExport Citation
Abstract
Authors
Article Text
  • ACKNOWLEDGMENTS
    • Supplemental Material
    References

    Abstract

    We present transport measurements on a dipolar superfluid using a Bose-Einstein condensate of Dy162 with strong magnetic dipole-dipole interactions. By moving an attractive laser beam through the condensate we observe an anisotropy in superfluid flow. This observation is compatible with an anisotropic critical velocity for the breakdown of dissipationless flow, which, in the spirit of the Landau criterion, can directly be connected to the anisotropy of the underlying dipolar excitation spectrum. In addition, the heating rate above this critical velocity reflects the same anisotropy. Our observations are in excellent agreement with simulations based on the Gross-Pitaevskii equation and highlight the effect of dipolar interactions on macroscopic transport properties, rendering dissipation anisotropic.

    • Figure
    • Figure
    • Received 12 April 2018

    DOI:https://doi.org/10.1103/PhysRevLett.121.030401

    © 2018 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Bose gasesBose-Einstein condensatesDipolar gases
    Condensed Matter, Materials & Applied PhysicsAtomic, Molecular & Optical

    Authors & Affiliations

    Matthias Wenzel, Fabian Böttcher, Jan-Niklas Schmidt, Michael Eisenmann, Tim Langen, Tilman Pfau, and Igor Ferrier-Barbut*

    • 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology (IQST), Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany

    • *i.ferrier-barbut@physik.uni-stuttgart.de

    Article Text (Subscription Required)

    Click to Expand

    Supplemental Material (Subscription Required)

    Click to Expand

    References (Subscription Required)

    Click to Expand
    Issue

    Vol. 121, Iss. 3 — 20 July 2018

    Reuse & Permissions
    Access Options
    Author publication services for translation and copyediting assistance advertisement

    Authorization Required

    Log In
    Other Options
    ×

    Images

    • Figure 1
      Figure 1

      Probing anisotropic critical velocity. (a) Excitation spectrum of a homogeneous dipolar Bose gas. The speed of sound vs depends on the direction of the excitation k with respect to the dipole polarization B, denoted by the angle α. (b) The critical velocity vc (solid), as given by Eq. (2), becomes anisotropic and is in general lower than vs (dashed). (c) Schematic of the experiment. We drag an attractive laser beam through a dipolar condensate perpendicular (α=90°, blue) and parallel (α=0°, red) to the magnetic field direction.

      Reuse & Permissions
    • Figure 2
      Figure 2

      Temperature of the dBEC after stirring for (a) the isotropic case with B∥z^ and (b) the anisotropic case with B∥x^ in an almost cylindrical trap. In (c) the trap is additionally reshaped to invert the cloud aspect ratio. The stirring beam is moved along the x (red squares) or y (blue circles) axis, as illustrated in the insets with example in situ images. Critical velocities are extracted by a linear fit (dashed) and marked with arrows. In (a) the response is isotropic with vx=0.20(5) and vy=0.20(7)  mm/s, while we observe a clear difference in (b) with v⊥=0.16(2)  mm/s along y^ and v∥=0.36(3)  mm/s along x^. In (c) we extract v⊥=0.12(3) and v∥=0.26(4)  mm/s proving that the observed anisotropy remains even when inverting the anisotropy of the atomic cloud. Data points with stirring frequency matching the trapping frequencies (gray) are excluded from the analysis. Simulations of the eGPE for a single stirring cycle (solid lines) show excellent agreement with the experiment. See text for further parameters.

      Reuse & Permissions
    ×

    Sign up to receive regular email alerts from Physical Review Letters

    Log In

    Cancel
    ×

    Search

    Article Lookup

    Paste a citation or DOI
    Enter a citation
    ×