Thermal friction on quantum vortices in a Bose-Einstein condensate

Moon, Geol; Kwon, Woo Jin; Lee, Hyunjik; Shin, Yeong Gil

doi:10.1103/physreva.92.051601

Cited by 46 publications

(58 citation statements)

References 50 publications

(82 reference statements)

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“…[39] gives a timescale that is consistent with our simulation. We also note that the vortex lifetime is suppressed at high tempearures [40][41][42].…”

Section: B Vortex Dynamicsmentioning

confidence: 78%

Superfluidity and relaxation dynamics of a laser-stirred two-dimensional Bose gas

et al. 2017

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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 et al., Nat. Phys. 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 vc, 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.

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“…[39] gives a timescale that is consistent with our simulation. We also note that the vortex lifetime is suppressed at high tempearures [40][41][42].…”

Section: B Vortex Dynamicsmentioning

confidence: 78%

Superfluidity and relaxation dynamics of a laser-stirred two-dimensional Bose gas

et al. 2017

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“…In recent years, there have been indirect experimental evidence [2] and tantalizing numerical results [3][4][5] of the existence of an inverse energy cascade that follows the Kolmogorov scaling analogously to the classical turbulence. The condensation of energy on large scales has also been investigated in decaying quantum turbulence [6][7][8]. A crucial link between these two phenomena is that there is a net transport of energy from small to large scales and this happens in quantum turbulence due to the spatial clustering of quantized vortices of the same circulation.…”

Section: Introductionmentioning

confidence: 99%

Origin of the inverse energy cascade in two-dimensional quantum turbulence

Skaugen

Angheluta

2017

Phys. Rev. E

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We establish a statistical relationship between the inverse energy cascade and the spatial correlations of clustered vortices in two-dimensional quantum turbulence. The Kolmogorov spectrum k −5/3 on inertial scales r corresponds to a pair correlation function between the vortices with different signs that decays as a power law with the pair distance given as r −4/3 . To test these scaling relations, we propose a forced and dissipative point vortex model that captures the turbulent dynamics of quantized vortices by the emergent clustering of same-sign vortices. The inverse energy cascade developing in a statistically neutral system originates from this vortex clustering that evolves with time.

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“…In atomic BECs the point-vortex model provides an excellent description of vortex dynamics in a hydrodynamic regime [29][30][31][32]. Furthermore, experimental observations of small-scale clustering [33,34], and Gross-Pitaevskii simulations demonstrating clustering in forced [35,36] and decaying [37] homogeneous systems, in harmonic traps [38], and disk geometries [39] have raised the prospect that large-scale clustered states may be realized, amid increasing theoretical [40][41][42][43][44][45][46][47][48][49] and experimental [32,[50][51][52][53] interest.…”

Section: B Motivation From Bose-einstein Condensatesmentioning

confidence: 99%

Theory of the vortex-clustering transition in a confined two-dimensional quantum fluid

Billam

Nian

et al. 2016

Phys. Rev. A

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Clustering of like-sign vortices in a planar bounded domain is known to occur at negative temperature, a phenomenon that Onsager demonstrated to be a consequence of bounded phase space. In a confined superfluid, quantized vortices can support such an ordered phase, provided they evolve as an almost isolated subsystem containing sufficient energy. A detailed theoretical understanding of the statistical mechanics of such states thus requires a microcanonical approach. Here we develop an analytical theory of the vortex clustering transition in a neutral system of quantum vortices confined to a two-dimensional disk geometry, within the microcanonical ensemble. The choice of ensemble is essential for identifying the correct thermodynamic limit of the system, enabling a rigorous description of clustering in the language of critical phenomena. As the system energy increases above a critical value, the system develops global order via the emergence of a macroscopic dipole structure from the homogeneous phase of vortices, spontaneously breaking the Z 2 symmetry associated with invariance under vortex circulation exchange, and the rotational SO(2) symmetry due to the disk geometry. The dipole structure emerges characterized by the continuous growth of the macroscopic dipole moment which serves as a global order parameter, resembling a continuous phase transition. The critical temperature of the transition, and the critical exponent associated with the dipole moment, are obtained exactly within mean-field theory. The clustering transition is shown to be distinct from the final state reached at high energy, known as supercondensation. The dipole moment develops via two macroscopic vortex clusters and the cluster locations are found analytically, both near the clustering transition and in the supercondensation limit. The microcanonical theory shows excellent agreement with Monte Carlo simulations, and signatures of the transition are apparent even for a modest system of 100 vortices, accessible in current Bose-Einstein condensate experiments.

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Thermal friction on quantum vortices in a Bose-Einstein condensate

Cited by 46 publications

References 50 publications

Superfluidity and relaxation dynamics of a laser-stirred two-dimensional Bose gas

Superfluidity and relaxation dynamics of a laser-stirred two-dimensional Bose gas

Origin of the inverse energy cascade in two-dimensional quantum turbulence

Theory of the vortex-clustering transition in a confined two-dimensional quantum fluid

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