Superfluidity and relaxation dynamics of a laser-stirred 2D Bose gas

Abstract

We investigate the superfluid behavior of a two-dimensional (2D) Bose gas of ${}^{87}$Rb atoms using classical field dynamics. In the experiment by R. Desbuquois \textit{et al.}, Nat. Phys. \textbf{8}, 645 (2012), a 2D quasicondensate in a trap is stirred by a blue-detuned laser beam along a circular path around the trap center. Here, we study this experiment from a theoretical perspective. The heating induced by stirring increases rapidly above a velocity $v_c$, which we define as the critical velocity. We identify the superfluid, the crossover, and the thermal regime by a finite, a sharply decreasing, and a vanishing critical velocity, respectively. We demonstrate that the onset of heating occurs due to the creation of vortex-antivortex pairs. A direct comparison of our numerical results to the experimental ones shows good agreement, if a systematic shift of the critical phase-space density is included. We relate this shift to the absence of thermal equilibrium between the condensate and the thermal wings, which were used in the experiment to extract the temperature. We expand on this observation by studying the full relaxation dynamics between the condensate and the thermal cloud.

11 pages, 9 figures, 1 table

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• Observation of the BKT Transition in a 2D Bose Gas via Matter-Wave Interferometry
• Superfluid density and critical velocity near the fermionic Berezinskii-Kosterlitz-Thouless transition
• Universal Scaling of the Dynamic BKT Transition in Quenched 2D Bose Gases
• Josephson junction dynamics in a two-dimensional ultracold Bose gas
• Collisionless Dynamics in Two-Dimensional Bosonic Gases
• Superfluidity of a laser-stirred Bose-Einstein condensate
• Minimum critical velocity of a Gaussian obstacle in a Bose-Einstein condensate
• Collective modes and superfluidity of a two-dimensional ultracold Bose gas
• Sound propagation in a two-dimensional Bose gas across the superfluid transition
• Critical velocity of a two-dimensional superflow past a potential barrier of arbitrary penetrability
• Critical velocity for superfluidity in the one-dimensional mean-field regime: From matter to light quantum fluids
• Thermal suppression of demixing dynamics in a binary condensate
• Observation of a Bilayer Superfluid with Interlayer Coherence
• Berezinskii-Kosterlitz-Thouless phase induced by dissipating quasisolitons
• First and second sound in a dilute Bose gas across the BKT transition
• Light-induced localized vortices in multicomponent Bose-Einstein condensates
• Realizing an Atomtronic AQUID in a Rotating-Box Potential
• Josephson Dynamics in 2D Ring-shaped Condensates
• Influence of quantum fluctuations on the superfluid critical velocity of a one-dimensional Bose gas