Nonclassical Velocity Statistics in a Turbulent Atomic Bose-Einstein Condensate

White, Angela; Barenghi, Carlo F.; Proukakis, N. P.; Youd, Anthony J.; Wacks, Daniel H.

doi:10.1103/physrevlett.104.075301

Cited by 118 publications

(146 citation statements)

References 39 publications

(29 reference statements)

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“…Figure 1 (right) thus also confirms the non-Gaussian (hence non-classical) nature of the velocity PDFs due to the quantised nature of the vortices [5,28,40,44]. We have also considered (see Fig.…”

Section: Fig 1: Tangle Of Few Interacting Vortices (Left) Exhibitingsupporting

confidence: 58%

“…With regards to quantum turbulence, a landmark experiment recently generated a small tangle of vortices in a trapped weakly-interacting BEC through the combination of rotation and an external oscillating perturbation [22][23][24]. Several theoretical works have studied the statistical properties of vortex tangles in three-dimensional (3D) superfluid systems [25][26][27][28]. Another proposed method to generate a vortex tangle combines rotations about two different axes [29].…”

Section: Fig 1: Tangle Of Few Interacting Vortices (Left) Exhibitingmentioning

confidence: 99%

“…This is an artifact of the method for calculating the vortex length, which measures it within a fixed spherical volume, (4π/3)R 3 cut , where R cut = 0.78R TF . The entire condensate undergoes volume oscillations [28], and vortices move in and out of the region where the length is determined. The dominant frequency of this linelength oscillation is approximately 2.2ω which is close to the frequency of the monopole mode (ω osc = √ 5ω in the TF approximation [50]) of a harmonically-trapped BEC [39,41].…”

Section: Fig 1: Tangle Of Few Interacting Vortices (Left) Exhibitingmentioning

confidence: 99%

“…It is difficult to determine by visual inspection how isotropic a vortex tangle is [28]. To measure it precisely, we compute the probability density function (normalised histogram, or PDF for short) of the velocity components v x , v y and v z .…”

Section: Fig 1: Tangle Of Few Interacting Vortices (Left) Exhibitingmentioning

confidence: 99%

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Isotropic vortex tangles in trapped atomic Bose-Einstein condensates via laser stirring

et al. 2014

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The generation of isotropic vortex configurations in trapped atomic Bose-Einstein condensates offers a platform to elucidate quantum turbulence on mesoscopic scales. We demonstrate that a laser-induced obstacle moving in a figure-eight path within the condensate provides a simple and effective means to generate an isotropic three-dimensional vortex tangle due to its minimal net transfer of angular momentum to the condensate. Our characterisation of vortex structures and their isotropy is based on projected vortex lengths and velocity statistics obtained numerically via the Gross-Pitaevskii equation. Our methodology provides a possible experimental route for generating and characterising vortex tangles and quantum turbulence in atomic Bose-Einstein condensates. Vortices in ordinary (classical) fluids, as well as quantum fluids, characterise turbulent flow [1,2]. Turbulence in classical fluids has been intensely studied in many branches of physics and engineering over a prolonged period. Characterising turbulence and understanding its dynamics is one of the key goals of these fields. Homogeneous, isotropic turbulence is the benchmark to understand vortex dynamics away from boundaries. Quantum fluids, such as superfluid He and atomic BoseEinstein condensates (BECs), where the circulation is quantized and viscosity is absent, open up the possibility of a context in which to study turbulence which is simpler than in ordinary fluids. Large vortex tangles have been created experimentally in superfluid He for this purpose. The investigation of the properties of such systems has revealed, for certain parameter regimes, the emergence of classical-like behaviour (such as the Kolmogorov scaling [3-5] of the energy spectrum for homogeneous isotropic turbulence) from the dynamics of elementary quantum vortices.Usually terms like "turbulence" and "vortex tangles" refer to disordered fluid systems containing vortices and eddies in which a huge range of lengthscales and timescales are excited; scaling laws therefore can be identified. Unlike ordinary fluids and superfluid helium, atomic BECs are relatively small, in the sense that there is not a large separation of lengthscales between the vortex core size, the average intervortex separation and the system size [6]. An important question which should be addressed in this context, is whether a relatively small vortex configuration exhibits turbulent properties, or it is simply chaotic. A first step in addressing this question is to demonstrate a technique for generating a few interacting vortices (see Fig. 1 (left)) that give isotropic flow statistics (see Fig. 1 (right)), which is the main result of this paper. * Electronic address: carlo.barenghi@ncl.ac.uk FIG. 1: Tangle of few interacting vortices (left) exhibiting isotropic non-Gaussian flow statistics (right). Left: Density isosurface generated by stirring a spherically symmetric condensate along one plane in a figure-eight path (at time t ≈ tstir = 17.1ω −1 when the stirrer has just been removed after approximately two osci...

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Section: Fig 1: Tangle Of Few Interacting Vortices (Left) Exhibitingsupporting

confidence: 58%

Section: Fig 1: Tangle Of Few Interacting Vortices (Left) Exhibitingmentioning

confidence: 99%

Section: Fig 1: Tangle Of Few Interacting Vortices (Left) Exhibitingmentioning

confidence: 99%

Section: Fig 1: Tangle Of Few Interacting Vortices (Left) Exhibitingmentioning

confidence: 99%

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Isotropic vortex tangles in trapped atomic Bose-Einstein condensates via laser stirring

et al. 2014

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“…This behavior has been linked to vortex reconnections [7], even though it can be obtained also when vortex reconnections do not occur, such as in two-dimensional classical vortex points systems [13]. The non-gaussian velocity distribution can however be seen as a fundamental property of quantum turbulence, supporting the quantum mechanical description of superfluid 4 He as containing a tangle of quantized vortices.…”

Section: Resultsmentioning

confidence: 95%

Lagrangian velocity distributions in thermal counterflow of superfluid⁴He

Mantia

Duda

Rotter

et al. 2013

EPJ Web of Conferences

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Abstract. Quantum turbulence in thermal counterflow of superfluid 4 He is visualized and studied at length scales comparable to the average distance between quantized vortices. The lagrangian velocities of micrometersized deuterium particles are obtained in a planar section of the flow field by using the particle tracking velocimetry technique. It is shown that the lagrangian velocity normalized distributions are strongly non-gaussian, with power-law tails, in contrast to the nearly gaussian distributions obtained in classical turbulent flows. The average distance between quantized vortices can therefore be seen as the length scale indicating the transition between classical-like and quantum behavior in thermal counterflow of superfluid 4 He.

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A Primer on Quantum Fluids

Barenghi

Parker²

2016

SpringerBriefs in Physics

104

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PrefaceThis book introduces the theoretical description and properties of quantum fluids. The focus is on gaseous atomic Bose-Einstein condensates and, to a minor extent, superfluid helium, but the underlying concepts are relevant to other forms of quantum fluids such as polariton and photonic condensates. The book is pitched at the level of advanced undergraduates and early postgraduate students, aiming to provide the reader with the knowledge and skills to develop their own research project on quantum fluids. Indeed, the content for this book grew from introductory notes provided to our own research students. It is assumed that the reader has prior knowledge of undergraduate mathematics and/or physics; otherwise, the concepts are introduced from scratch, often with references for directed further reading.After an overview of the history of quantum fluids and the motivations for studying them (Chapter 1), we introduce the simplest model of a quantum fluid provided by the ideal Bose gas, following the seminal works of Bose and Einstein (Chapter 2). The Gross-Pitaevskii equation, an accurate description of weakly-interacting Bose gases at low temperatures, is presented, and its typical time-independent solutions examined (Chapter 3). We then progress to solitons and waves (Chapter 4) and vortices (Chapter 5) in quantum fluids. For important aspects which fall outside the scope of this book, e.g. modelling of Bose gases at finite temperatures, we list appropriate reading material. Each chapter ends with key exercises to deepen the understanding. Detailed solutions can be made available to instructors upon request to the authors.We thank Nick Proukakis and Em Rickinson for helpful comments on this work.

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Nonclassical Velocity Statistics in a Turbulent Atomic Bose-Einstein Condensate

Cited by 118 publications

References 39 publications

Isotropic vortex tangles in trapped atomic Bose-Einstein condensates via laser stirring

Isotropic vortex tangles in trapped atomic Bose-Einstein condensates via laser stirring

Lagrangian velocity distributions in thermal counterflow of superfluid⁴He

A Primer on Quantum Fluids

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Nonclassical Velocity Statistics in a Turbulent Atomic Bose-Einstein Condensate

Cited by 118 publications

References 39 publications

Isotropic vortex tangles in trapped atomic Bose-Einstein condensates via laser stirring

Isotropic vortex tangles in trapped atomic Bose-Einstein condensates via laser stirring

Lagrangian velocity distributions in thermal counterflow of superfluid4He

A Primer on Quantum Fluids

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Lagrangian velocity distributions in thermal counterflow of superfluid⁴He