First and second sound in a two-dimensional harmonically trapped Bose gas across the Berezinskii–Kosterlitz–Thouless transition

Liu, Xia-Ji; Hu, Hui

doi:10.1016/J.AOP.2014.08.023

Title: First and second sound in a two-dimensional harmonically trapped Bose gas across the Berezinskii–Kosterlitz–Thouless transition

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Abstract

We theoretically investigate first and second sound of a two-dimensional (2D) atomic Bose gas in harmonic traps by solving Landau’s two-fluid hydrodynamic equations. For an isotropic trap, we find that first and second sound modes become degenerate at certain temperatures and exhibit typical avoided crossings in mode frequencies. At these temperatures, second sound has significant density fluctuation due to its hybridization with first sound and has a divergent mode frequency towards the Berezinskii–Kosterlitz–Thouless (BKT) transition. For a highly anisotropic trap, we derive the simplified one-dimensional hydrodynamic equations and discuss the sound-wave propagation along the weakly confined direction. Due to the universal jump of the superfluid density inherent to the BKT transition, we show that the first sound velocity exhibits a kink across the transition. These predictions might be readily examined in current experimental setups for 2D dilute Bose gases with a sufficiently large number of atoms, where the finite-size effect due to harmonic traps is relatively weak.

Authors:: Liu, Xia-Ji; Hu, Hui

Publication Date:: Mon Dec 15 00:00:00 EST 2014

OSTI Identifier:: 22403482

Resource Type:: Journal Article

Journal Name:: Annals of Physics (New York)

Additional Journal Information:: Journal Volume: 351; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0003-4916

Country of Publication:: United States

Language:: English

Subject:: 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BOSE-EINSTEIN GAS; HYBRIDIZATION; HYDRODYNAMICS; ONE-DIMENSIONAL CALCULATIONS; PHASE TRANSFORMATIONS; SECOND SOUND; SOUND WAVES; SUPERFLUIDITY; TRAPPING; TWO-DIMENSIONAL CALCULATIONS; TWO-DIMENSIONAL SYSTEMS; WAVE PROPAGATION

Citation Formats


                    Liu, Xia-Ji, and Hu, Hui. First and second sound in a two-dimensional harmonically trapped Bose gas across the Berezinskii–Kosterlitz–Thouless transition.  United States: N. p., 2014. 
        Web.  doi:10.1016/J.AOP.2014.08.023.

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                    Liu, Xia-Ji, & Hu, Hui. First and second sound in a two-dimensional harmonically trapped Bose gas across the Berezinskii–Kosterlitz–Thouless transition.  United States.  https://doi.org/10.1016/J.AOP.2014.08.023

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                    Liu, Xia-Ji, and Hu, Hui. 2014.  
        "First and second sound in a two-dimensional harmonically trapped Bose gas across the Berezinskii–Kosterlitz–Thouless transition".  United States.  https://doi.org/10.1016/J.AOP.2014.08.023.

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@article{osti_22403482,

  title        = {First and second sound in a two-dimensional harmonically trapped Bose gas across the Berezinskii–Kosterlitz–Thouless transition},

  author       = {Liu, Xia-Ji and Hu, Hui},

  abstractNote = {We theoretically investigate first and second sound of a two-dimensional (2D) atomic Bose gas in harmonic traps by solving Landau’s two-fluid hydrodynamic equations. For an isotropic trap, we find that first and second sound modes become degenerate at certain temperatures and exhibit typical avoided crossings in mode frequencies. At these temperatures, second sound has significant density fluctuation due to its hybridization with first sound and has a divergent mode frequency towards the Berezinskii–Kosterlitz–Thouless (BKT) transition. For a highly anisotropic trap, we derive the simplified one-dimensional hydrodynamic equations and discuss the sound-wave propagation along the weakly confined direction. Due to the universal jump of the superfluid density inherent to the BKT transition, we show that the first sound velocity exhibits a kink across the transition. These predictions might be readily examined in current experimental setups for 2D dilute Bose gases with a sufficiently large number of atoms, where the finite-size effect due to harmonic traps is relatively weak.},

  doi          = {10.1016/J.AOP.2014.08.023},

  url          = {https://www.osti.gov/biblio/22403482},
  journal      = {Annals of Physics (New York)},

  issn         = {0003-4916},

  number       = ,

  volume       = 351,

  place        = {United States},

  year         = {Mon Dec 15 00:00:00 EST 2014},

  month        = {Mon Dec 15 00:00:00 EST 2014}

}

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