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  • Featured in Physics
  • Open Access

Observation of Anisotropic Superfluid Density in an Artificial Crystal

J. Tao*, M. Zhao*, and I. B. Spielman

  • Joint Quantum Institute, University of Maryland and National Institute of Standards and Technology, College Park, Maryland 20742, USA

  • *These two authors contributed equally.
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Phys. Rev. Lett. 131, 163401 – Published 18 October, 2023

DOI: https://doi.org/10.1103/PhysRevLett.131.163401

Abstract

We experimentally and theoretically investigate the anisotropic speed of sound of an atomic superfluid (SF) Bose-Einstein condensate in a 1D optical lattice. Because the speed of sound derives from the SF density, this implies that the SF density is itself anisotropic. We find that the speed of sound is decreased by the optical lattice, and the SF density is concomitantly reduced. This reduction is accompanied by the appearance of a zero entropy normal fluid in the purely Bose condensed phase. The reduction in SF density—first predicted [A. J. Leggett, Phys. Rev. Lett. 25, 1543 (1970).] in the context of supersolidity—results from the coexistence of superfluidity and density modulations, but is agnostic about the origin of the modulations. We additionally measure the moment of inertia of the system in a scissors mode experiment, demonstrating the existence of rotational flow. As such we shed light on some supersolid properties using imposed, rather than spontaneously formed, density order.

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synopsis

Cold Atoms Link a BEC, a Superfluid, and a Supersolid

Published 18 October, 2023

Trapping a Bose-Einstein condensate (BEC) in an optical lattice, researchers confirm a 53-year-old theory that connects BECs to superfluids and supersolids.

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Supplemental Material

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Outline

Information

Phys. Rev. Lett. 131, 163401– Published 18 October, 2023
  • Received 21 December 2022
  • Accepted 7 August 2023
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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