Persistent currents in two-component condensates in a toroidal trap

Abad, M.; Sartori, Alberto; Finazzi, Stefano; Recati, Alessio

doi:10.1103/physreva.89.053602

Cited by 32 publications

(50 citation statements)

References 40 publications

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“…The BECs with a CR vortex are expected to be closely related to counter-superflow because the BECs with a CR vortex and counter-superflow have similarity, such as relative motion. Counter-rotating binary BECs have been theoretically studied in a toroidal trap [20,26]. Our work focuses on natures of counter-rotating systems as a vortex in a harmonic oscillator potential.…”

Section: Introductionmentioning

confidence: 99%

Counter-rotating vortices in miscible two-component Bose-Einstein condensates

2013

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Counter-rotating vortices in miscible two-component Bose-Einstein condensates, in which superflows counter-rotate between the two components around the overlapped vortex cores, are studied theoretically in a pancake-shaped potential. In a linear stability analysis with the Bogoliubov-de Gennes model, we show that counter-rotating vortices are dynamically unstable against splitting into multiple vortices. The instability shows characteristic behaviors as a result of counter-superflow instability, which causes relaxation of relative flows between the two components in binary condensates. The characteristic behaviors are completely different from those of multiquantum vortices in single-component Bose-Einstein condensates; the number of vortices generated by the instability can become larger than the initial winding number of the counter-rotating vortex. We also investigate the nonlinear dynamics of the instability by numerically solving the Gross-Pitaevskii equations. The nonlinear dynamics drastically changes when the winding number of counter-rotating vortices becomes larger, which lead to nucleation of vortex pairs outside of the vortex core. The instability eventually develops into turbulence after the relaxation of the relative rotation between the two components.

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Section: Introductionmentioning

confidence: 99%

Counter-rotating vortices in miscible two-component Bose-Einstein condensates

2013

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“…For trapped condensates these values are slightly shifted due to the inhomogeneous density profile [18,19] and the density distribution in the phase separated regime is determined by the shape of the external trapping potential. In narrow ring traps (and when g 11 = g 22 ), azimuthal phase separation is favoured (see for instance [5,20,21]), while in wider toroidal traps concentric ring configurations can occur (see for instance [20,21]). In the following we numerically solve the coupled GP equations by applying a pseudo-spectral second order Strang method with symmetric three-operator splitting [22].…”

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confidence: 99%

Emergence of classical rotation in superfluid Bose-Einstein condensates

2016

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Phase transitions can modify quantum behaviour on mesoscopic scales and give access to new and unusual quantum dynamics. Here we investigate the superfluid properties of a rotating twocomponent Bose-Einstein condensate as a function of changes in the interaction energy and in particular through the phase transition from miscibility to immiscibility. We show that the breaking of one of the hallmarks of superfluid flow, namely the quantisation condition on circulation, is continuous throughout an azimuthal phase separation process and displays intriguing density dynamics. We find that the resulting currents are stable for long times and possess a phase boundary that exhibits classical solid body rotation, despite the quantum nature of superfluid flow. To support this co-existence of classical and quantum behaviour the system develops a unique velocity flow profile, which includes unusual radial flow in regions near the phase boundary.Phase transitions in quantum systems can have a dramatic impact on the quantum mechanical behaviour on mesoscopic scales. Superfluidity in Bose-condensed gases is a mesoscopic manifestation of quantum mechanical effects and one of its hallmarks is the existence of quantised flow around phase singularities as a response to external rotation [1][2][3][4]. However, as the quantisation condition arises from the requirement of the single-valuedness of the wavefunction, an interesting, and less well investigated, generalization appears in superfluids composed of several components. In these systems, due to the interplay of intra-and inter-component interactions, the spinor order parameter can undergo a phase transition that modifies the global symmetry of the system. As the quantisation condition applies to each component independently, the path along which circulation is determined consequently depends on the presence of the other component. This has proven to be particularly striking in toroidally trapped binary mixtures of BECs, where immiscibility can drive a transition to azimuthal phase separation, breaking the requirement of quantised circulation around the toroid [5]. Below we show that this transition is continuous and leads to a phase boundary, which rotates as a classical solid body. While this might seem at first to be incompatible with the quantum nature of superfluid flow, this co-existence can be explained through the presence of a radial flow.In superfluids the circulation around a closed path p is quantised according to p v · dr = n2π /m . Here n is an integer winding number, m the atomic mass, the reduced Planck constant, and the superfluid velocity field, v = ∇θ/m, is completely determined by the gradient of the condensate phase, θ. This implies the velocity field of a vortex has a tangential 1/r velocity profile, in contrast to classical rigid-body rotation, where v = Ω × r. The creation of vortices is a response to external rotation and depends, in particular, on the confining geometry. While in simply connected trapping potentials vortices with higher winding numbers a...

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“…The atoms interact via a contact interaction with strengths U AA , U BB and U AB . Quantitative studies of this system have been done only by variational methods in the limit of equal [10][11][12][13][14] and unequal [15] interaction strengths.…”

Section: Introductionmentioning

confidence: 99%

Mixture of two ultra cold bosonic atoms confined in a ring: stability and persistent currents

Matsushita

Passos

2018

J. Phys. Commun.

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In this article we investigate the stability of quantized yrast states in a mixture of two distinguishable equal mass bosonic atoms confined in a ring. We focus in the study of energetic stability since the Bloch analysis and the Bogoliubov theory establishes that only energetically stable quantized yrast states are capable of sustain a persistent current. In the framework of the Bogoliubov theory we study the stability in two different cases chosen by physical considerations. In one case we analyze how the inter and intraspecies interaction strengths affect the stability of a selected quantized yrast state specified by the angular momentum per particle and the population imbalance. In the other case, for a fixed dynamics specified by given values of interaction strengths, we determine the stability of quantized yrast states as function of the angular momentum per particle and the population imbalance. We also examined the stability of the mixture in the rarefied limit and we found a critical value of the population imbalance which gives the size of the window of energetic stability and a critical value of angular momentum per particle which is an upper bound of the possible values of angular momentum per particle carried by energetically stable quantized yrast states.

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Persistent currents in two-component condensates in a toroidal trap

Cited by 32 publications

References 40 publications

Counter-rotating vortices in miscible two-component Bose-Einstein condensates

Counter-rotating vortices in miscible two-component Bose-Einstein condensates

Emergence of classical rotation in superfluid Bose-Einstein condensates

Mixture of two ultra cold bosonic atoms confined in a ring: stability and persistent currents

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