Second sound in 2D Bose gas: from the weakly interacting to the strongly interacting regime

Abstract

Using Landau's theory of two-fluid hydrodynamics, we investigate first and second sound propagating in a two-dimensional Bose gas. We study the temperature and interaction dependence of both sound modes and show that their behaviour exhibits a deep qualitative change as the gas evolves from the weakly interacting to the strongly interacting regime. Special emphasis is given to the jump of both sounds at the Berezinskii-Kosterlitz-Thouless transition, caused by the discontinuity of the superfluid density. We find that the excitation of second sound through a density perturbation becomes weaker and weaker as the interaction strength increases as a consequence of the decrease of the thermal expansion coefficient. Our results can be relevant for future experiments on the propagation of sound in the BEC side of the BCS-BEC crossover of a 2D superfluid Fermi gas.

14 pages, 6 figures

References in corpus (14)

• Many-Body Physics with Ultracold Gases
• Theory of ultracold Fermi gases
• Vortices and Superfluidity in a Strongly Interacting Fermi Gas
• Emergence of coherence in a uniform quasi-two-dimensional Bose gas
• Observation of scale invariance and universality in two-dimensional Bose gases
• Superfluid behaviour of a two-dimensional Bose gas
• Observation of the Berezinskii-Kosterlitz-Thouless Phase Transition in an Ultracold Fermi Gas
• Two-Dimensional Homogeneous Fermi Gases
• Critical velocity for superfluid flow across the BEC-BCS crossover
• Strongly Interacting Two-Dimensional Bose Gases
• First and second sound in a strongly interacting Fermi gas
• Universal thermodynamics of a two-dimensional Bose gas
• Superfluid density and critical velocity near the fermionic Berezinskii-Kosterlitz-Thouless transition
• Composite bosons in the 2D BCS-BEC crossover from Gaussian fluctuations

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• Low-energy collective oscillations and Bogoliubov sound in an exciton-polariton condensate
• Collisionless Dynamics in Two-Dimensional Bosonic Gases
• Signatures of a universal jump in the superfluid density in two-dimensional Bose gas with finite number of particles
• Sound propagation in a two-dimensional Bose gas across the superfluid transition
• Propagation of first and second sound in a two-dimensional Fermi superfluid
• Observation of Algebraic Time Order for Two-Dimensional Dipolar Excitons
• Second sound with ultracold atoms: A brief historical account
• Berezinskii-Kosterlitz-Thouless phase transition with Rabi-coupled bosons
• Sound modes in collisional superfluid Bose gases
• Dynamical Kosterlitz-Thouless Theory for Two-Dimensional Ultracold Atomic Gases
• Superfluid properties of bright solitons in a ring
• Berezinskii-Kosterlitz-Thouless phase induced by dissipating quasisolitons
• First and second sound in a dilute Bose gas across the BKT transition