Superfluid flow above the critical velocity

Paris-Mandoki, Asaf; Shearring, J.; Mancarella, Francesco; Fromhold, T. M.; Trombettoni, Andrea; Krüger, Peter

doi:10.1038/s41598-017-08941-8

Cited by 12 publications

(9 citation statements)

References 44 publications

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“…We showcase the latter by simulating in-situ single shot images upon considering a fairly large bosonic cloud. Finally, we retrieve superfluidity for high speed impurities [65] namely for velocities being almost six times the bulk (i.e. the maximal value measured around the trap center) speed of sound.…”

Section: Introductionmentioning

confidence: 99%

Many-body dissipative flow of a confined scalar Bose-Einstein condensate driven by a Gaussian impurity

et al. 2018

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The many-body dissipative flow induced by a mobile Gaussian impurity harmonically oscillating within a cigar-shaped Bose-Einstein condensate is investigated. For very small and large driving frequencies the superfluid phase is preserved. Dissipation is identified, for intermediate driving frequencies, by the non-zero value of the drag force whose abrupt increase signals the spontaneous downstream emission of an array of gray solitons. After each emission event, typically each of the solitary waves formed decays and splits into two daughter gray solitary waves that are found to be robust propagating in the bosonic background for large evolution times. In particular, a smooth transition towards dissipation is observed, with the critical velocity for solitary wave formation depending on both the characteristics of the obstacle, namely its driving frequency and width as well as on the interaction strength. The variance of a sample of single-shot simulations indicates the fragmented nature of the system; here it is found to increase during evolution for driving frequencies where the coherent structure formation becomes significant. Finally, we demonstrate that for fairly large particle numbers in-situ single-shot images directly capture the gray soliton's decay and splitting. arXiv:1805.08618v2 [cond-mat.quant-gas]

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Section: Introductionmentioning

confidence: 99%

Many-body dissipative flow of a confined scalar Bose-Einstein condensate driven by a Gaussian impurity

et al. 2018

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“…One could wonder how a localized defect would dissipate a superfluid flow at such a supersonic speed. This would complete to even higher speeds the theoretical and recent experimental works [44][45][46][47][48] that have shown that obstacles moving at velocities far exceeding the Landau critical velocity do not necessarily create a significant amount of excitations.…”

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confidence: 92%

“…This suggest the need of more refined theoretical models beyond the diffuse vorticity approximation and stimulates further experimental investigation of the excitation spectrum. The creation of this rotating state offers fascinating perspectives for the study of supercritical flows [18,46,47].…”

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confidence: 99%

Supersonic Rotation of a Superfluid: A Long-Lived Dynamical Ring

et al. 2020

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We present the experimental realization of a long-lived superfluid flow of a quantum gas rotating in an anharmonic potential, sustained by its own angular momentum. The gas is set into motion by rotating an elliptical deformation of the trap. An evaporation selective in angular momentum yields an acceleration of rotation until the density vanishes at the trap center, resulting in a dynamical ring with 350 angular momentum per particle. The density profile of the ring corresponds to the one of a quasi two-dimensional superfluid, with a linear velocity reaching Mach 18 and a rotation lasting more than a minute.Superfluidity is a rich quantum dynamical phenomenon first observed in low temperature helium that also occurs for interacting degenerate gases [1]. Among its most striking manifestations are the existence of a critical velocity for the creation of excitations [2] and the appearance of quantized vortices when set into rotation, as has been observed in liquid helium [3] and in dilute Bose-Einstein condensates (BEC) [4,5].Because of a formal analogy between the two Hamiltonians, a neutral gas in rotation is a natural candidate to simulate a quantum system of charged particles in a magnetic field, relevant for condensed matter problems such as type II superconductors or the quantum Hall effect [6,7]. For a quantum gas confined in a harmonic trap of radial frequency ω r and rotating at angular frequency Ω approaching ω r , the ground state of the system reaches the atomic analog of the Lowest Landau Level (LLL) relevant in the quantum Hall regime [8][9][10]. The LLL has been reached for a dilute BEC [11] rotating at Ω = 0.993 ω r where dynamical properties of the system are modified compared with the mean-field regime.For rotation rates even closer to ω r , the formation of highly correlated states is predicted, similar to the ones involved in the fractional quantum Hall regime, such as Laughlin states [12] or Moore-Read states [13]. Reaching these fast rotation rates is experimentally challenging in a harmonic trap because the radial effective trapping potential in the rotating frame vanishes due to the centrifugal force. To circumvent this limit, higher-order confining potentials have been developed [14], which allow to access the regime where Ω even exceeds ω r . Although the experimental study of highly correlated states seems very challenging [15][16][17], fast rotation in a two-dimensional harmonic-plus-quartic trap opens new physical regimes and has attracted a lot of attention [14,[18][19][20][21].In this situation, a zero-density area -a hole-grows at the trap center above a critical rotation frequency Ω h [22], leading to an annular two-dimensional density profile. Moreover, the velocity of the atomic flow is expected to be supersonic [18] i.e. exceeding by far the speed of 50 µm -2 0 2 4 6 8 10 Figure 1. (a) Computed density contour (red annulus) for a BEC rotating at 1.06 ωr in the shell trap (gray ellipsoid). (b) in situ integrated 2D density (in units of µm −2 ) of a dynamical ring rotating at Mach ...

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“…Motivated by the above remarks, we study the rotational properties of a Bose-Einstein condensed gas of atoms in the presence of an external potential [20][21][22][23][24][25][26][27][28][29]. We assume for simplicity that the atoms are confined in a ring potential, having in mind a very narrow annulus, or torus, where the transverse degrees of freedom are frozen.…”

Section: Introductionmentioning

confidence: 99%

Stationary states of Bose-Einstein condensed atoms rotating in an asymmetric ring potential

Ögren,

Drougakis,

Vasilakis

et al. 2021

Preprint

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We consider a Bose-Einstein condensate, which is confined in a very tight toroidal/annular trap, in the presence of a potential, which breaks the axial symmetry of the Hamiltonian. We investigate the stationary states of the condensate, when its density distribution co-rotates with the symmetry-breaking potential. As the strength of the potential increases, we have a gradual transition from vortex excitation to solid-body-like motion. Of particular importance are states where the system is static and yet it has a nonzero current/circulation, which is a realization of persistent currents/reflectionless potentials.

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Superfluid flow above the critical velocity

Cited by 12 publications

References 44 publications

Many-body dissipative flow of a confined scalar Bose-Einstein condensate driven by a Gaussian impurity

Many-body dissipative flow of a confined scalar Bose-Einstein condensate driven by a Gaussian impurity

Supersonic Rotation of a Superfluid: A Long-Lived Dynamical Ring

Stationary states of Bose-Einstein condensed atoms rotating in an asymmetric ring potential

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