First and second sound in a two-dimensional dilute Bose gas across the Berezinskii-Kosterlitz-Thouless transition
arXiv:1403.3484 · doi:10.1016/j.aop.2014.08.023
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. Our predictions can be readily examined in current experimental setups for 2D dilute Bose gases.
arXiv comment5 pages, 4 figures
References in corpus (24)
- Observation of scale invariance and universality in two-dimensional Bose gases
- Breathing Modes and Hidden Symmetry of Trapped Atoms in 2D
- Critical Point of a Weakly Interacting Two-Dimensional Bose Gas
- Precision Measurements of Collective Oscillations in the BEC-BCS Crossover
- Radiofrequency spectroscopy of a strongly interacting two-dimensional Fermi gas
- Superfluid behaviour of a two-dimensional Bose gas
- Observation of a two-dimensional Fermi gas of atoms
- Two-Dimensional Weakly Interacting Bose Gas in the Fluctuation Region
- Exploring the thermodynamics of a two-dimensional Bose gas
- Collective modes and ballistic expansion of a Fermi gas in the BCS-BEC crossover
- Crossover from 2D to 3D in a weakly interacting Fermi gas
- Strongly Interacting Two-Dimensional Bose Gases
- Collective Modes in a Unitary Fermi Gas across the Superfluid Phase Transition
- Sound propagation in a Bose-Einstein condensate at finite temperatures
- First and second sound in a strongly interacting Fermi gas
- Universal thermodynamics of a two-dimensional Bose gas
- Density distribution of a trapped two-dimensional strongly interacting Fermi gas
- Two-fluid hydrodynamic modes in a trapped superfluid gas
- First and second sound in a highly elongated Fermi gas at unitarity
- Discontinuities in the First and Second Sound Velocities at the Berezinskii-Kosterlitz-Thouless Transition
- Second sound and the density response function in uniform superfluid atomic gases
- First and second sound in cylindrically trapped gases
- Variational theory of two-fluid hydrodynamic modes at unitarity
- Renormalization-group flow and asymptotic behaviors at the Berezinskii-Kosterlitz-Thouless transitions