Critical velocity for vortex shedding in a Bose-Einstein condensate

Kwon, Woo Jin; Moon, Geol; Seo, Sang Won; Shin, Yeong Gil

doi:10.1103/physreva.91.053615

Cited by 67 publications

(79 citation statements)

References 36 publications

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“…[27]. Because the condensate is in the P phase with U (1) symmetry and the multiply charged vortices are unstable to decay [28], it is ensured that the generated vortices are singly charged.…”

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confidence: 99%

Half-Quantum Vortices in an Antiferromagnetic Spinor Bose-Einstein Condensate

et al. 2015

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We report on the observation of half-quantum vortices (HQVs) in the easy-plane polar phase of an antiferromagnetic spinor Bose-Einstein condensate. Using in situ magnetization-sensitive imaging, we observe that pairs of HQVs with opposite core magnetization are generated when singly charged quantum vortices are injected into the condensate. The dynamics of HQV pair formation is characterized by measuring the temporal evolutions of the pair separation distance and the core magnetization, which reveals the short-range nature of the repulsive interactions between the HQVs. We find that spin fluctuations arising from thermal population of axial magnon excitations do not significantly affect the HQV pair formation dynamics. Our results demonstrate the instability of a singly charged vortex in the antiferromagnetic spinor condensate. In a scalar superfluid, the supercurrent circulation around quantum vortices is quantized in units of h/m due to U (1) gauge symmetry [1], where h is the Planck constant and m is particle mass. However, when a superfluid possesses an internal spin degree of freedom, there is an intriguing possibility for the superfluid to host quantum vortices of a fractional circulation of h/m. The superfluid phase interwinds with the spin orientation and a new relation is imposed on the supercurrent circulation in connection with spin texture [2]. Fractional quantum vortices are of particular interest in two-dimensional (2D) superfluidity. In the absence of long-range order in two dimensions [3], the superfluid phase transition in 2D is associated with vortex-antivortex pairing as described by the Berezinskii-Kosterlitz-Thouless (BKT) theory [4,5]. Hence fractional quantum vortices, introduced as new point defects, represent an interesting opportunity to explore for exotic superfluid phases, possibly beyond the BKT physics.Quantum vortices having h/2m circulation, so-called half-quantum vortices (HQVs) have been experimentally observed in spinor superfluid systems such as excitonpolariton condensates [6][7][8] and triplet superconductors [9]. In previous cold atom experiments, HQV states were created with an optical method in two-component Bose-Einstein condensates (BECs) [10], where the two components are not symmetric in terms of interactions. Recently, a spin-1 BEC with antiferromagnetic interactions has been considered with great interest because HQVs are topologically allowed in the polar phase of the system [11][12][13]. Theoretical studies predicted an anomalous superfluid density jump at the phase transition in two dimensions [14][15][16] as well as a new superfluid state that has completely broken spin ordering [17,18].In this Letter, we report on the observation of HQVs in the easy-plane polar phase of an antiferromagnetic spinor BEC of 23 Na atoms. Using magnetization-sensitive imaging, we observe that pairs of HQVs with opposite core magnetization are generated when singly charged quantum vortices are injected into the condensate. The temporal evolutions of the pair separation distance and t...

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confidence: 99%

Half-Quantum Vortices in an Antiferromagnetic Spinor Bose-Einstein Condensate

et al. 2015

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“…The experimental setup is similar to that in our previous work [11]. A highly oblate BEC of 23 Na atoms is prepared in a hybrid trap composed of a pancake-shaped optical trap and a magnetic quadruple trap.…”

Section: Methodsmentioning

confidence: 99%

“…Early theoretical works for 2D geometry anticipated periodic shedding of vortex dipoles from a moving circular obstacle [17][18][19][20][21], where the periodic shedding was depicted as a cycling process where the work done by a drag force from the moving obstacle accumulates to generate a quantized vortex dipole of a finite energy. However, in previous BEC experiments [9][10][11], periodic vortex shedding has never been observed, although the existence of a critical velocity was clearly demonstrated.…”

Section: Introductionmentioning

confidence: 99%

“…The periodic vortex generation might (b) Critical velocityṽc measured for fixed L.ṽc was determined from the data in (a), using the data analysis method described in Ref. [11]. The solid line is a linear fit to the data.…”

Section: Periodic Vortex Shedding a Penetrable Obstaclementioning

confidence: 99%

“…A vortex dipole is a pair of vortices of opposite circulations and its creation and annihilation are at the heart of many two-dimensional (2D) superfluid phenomena such as Berezinskii-Kosterlitz-Thouless superfluids [3,4], phase transition dynamics [5,6], and superfluid turbulence [7,8]. Quantized vortex dipoles were created in BECs by moving optical obstacles [9][10][11] and via quenching dynamics [12,13], and also observed in quasi-2D degenerate Bose gases [14]. Orbital motions of a single vortex dipole in a trapped BEC were investigated [10,13,15] and annihilation of vortex dipoles was indirectly probed in relaxation of superfluid turbulence in highly oblate BECs [16].…”

Section: Introductionmentioning

confidence: 99%

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Periodic shedding of vortex dipoles from a moving penetrable obstacle in a Bose-Einstein condensate

2015

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We investigate vortex shedding from a moving penetrable obstacle in a highly oblate Bose-Einstein condensate. The penetrable obstacle is formed by a repulsive Gaussian laser beam that has the potential barrier height lower than the chemical potential of the condensate. The moving obstacle periodically generates vortex dipoles and the vortex shedding frequency fv linearly increases with the obstacle velocity v as fv = a(v − vc), where vc is a critical velocity. Based on periodic shedding behavior, we demonstrate deterministic generation of a single vortex dipole by applying a short linear sweep of a laser beam. This method will allow further controlled vortex experiments such as dipole-dipole collisions.

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Elements of Vortex-Dipole Dynamics in a Nonuniform Bose–Einstein Condensate

Sakhel¹,

Sakhel

2016

J Low Temp Phys

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Critical velocity for vortex shedding in a Bose-Einstein condensate

Cited by 67 publications

References 36 publications

Half-Quantum Vortices in an Antiferromagnetic Spinor Bose-Einstein Condensate

Half-Quantum Vortices in an Antiferromagnetic Spinor Bose-Einstein Condensate

Periodic shedding of vortex dipoles from a moving penetrable obstacle in a Bose-Einstein condensate

Elements of Vortex-Dipole Dynamics in a Nonuniform Bose–Einstein Condensate

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