Manifestations of vortices during ultracold-atom propagation through waveguides

Bromley, Michael W. J.; Esry, B. D.

doi:10.1103/physreva.70.013605

Cited by 6 publications

(4 citation statements)

References 29 publications

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“…A number of the vortices increase with the junction length. Similar to the other configurations[6,20,21,34,66,[78][79][80], seeding of the vortices into the current density is a result of the strong intersubband interaction which adds a transverse component to the particle flow. In a particular case of the DD-DN-DD wave guide, a strength of the vortex varies with energy E; for example, as one continues to approach E min from the left, the vortex gradually dissolves, and at very small conductances it completely disappears (figure9(d)).…”

mentioning

confidence: 81%

A straight quantum wave guide with mixed Dirichlet and Neumann boundary conditions in uniform magnetic fields

Olendski¹,

Mikhailovska²

2007

J. Phys. A: Math. Theor.

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A straight quasi-one-dimensional Dirichlet wave guide with a Neumann window of length L on one or two confining surfaces is considered theoretically with and without perpendicular homogeneous magnetic field . It is shown that for the field-free case, a bound state in the continuum (BIC) for one Neumann window exists for some critical lengths only, while for the two Neumann segments symmetrically located on the opposite walls, due to the restored transverse symmetry of the system, BICs exist for the arbitrary L. Bound states lying below the fundamental propagation threshold of the Dirichlet strip survive any strength of the uniform magnetic field and do not depend on its direction. Moreover, an increasing field induces new bound states regularly arranged with the levels present at B = 0. For two Neumann windows, strong magnetic fields lead to the degeneracy of the adjacent odd and even bound states with their energies almost equal to each other and to their corresponding counterpart for one Neumann segment, which is explained by mapping the problem onto the field-free one or two purely attractive one-dimensional quantum wells with field-dependent depth. Miscellaneous magnetotransport characteristics of the structures are also considered; in particular, it is demonstrated that small fields applied to the channel with two Neumann windows destroy BICs by coupling them to the continuum states. This is manifested in the conductance-Fermi energy dependence by Fano resonances. Currents flowing in the wave guide are investigated too, and it is shown that current density patterns near the resonances form vortices which change their chirality as energy sweeps through the resonant region. Generalizations to any other arbitrary combination of the boundary conditions are provided. Comparison with other structures such as window-coupled Dirichlet wave guides, a bent strip or straight Dirichlet channel with electrostatic impurity inside, is performed.

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mentioning

confidence: 81%

A straight quantum wave guide with mixed Dirichlet and Neumann boundary conditions in uniform magnetic fields

Olendski¹,

Mikhailovska²

2007

J. Phys. A: Math. Theor.

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“…The scattering behavior for a well is complicated by the presence of bound states which translate into the presence of Feshbach resonances in a multichannel problem. Much of the resonance physics seen here has been extensively discussed as part of our studies of the circular waveguide bend [16,31]. The propagation thresholds in a bend lie slightly lower than the connecting leads [32,33], resulting in very weakly bound states and energetically narrow resonances.…”

Section: Well-like Waveguide Potentialmentioning

confidence: 91%

Transverse excitations of ultracold matter waves upon propagation past abrupt waveguide changes

2005

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The propagation of ultracold atomic gases through abruptly changing waveguide potentials is examined in the limit of noninteracting atoms. Time-independent scattering calculations of microstructured waveguides with discontinuous changes in the transverse harmonic binding potentials are used to mimic waveguide perturbations and imperfections. Three basic configurations are examined: steplike, barrierlike, and well-like with waves incident in the ground mode. At low energies, the spectra rapidly depart from single moded, with significant transmission and reflection of excited modes. The high-energy limit sees 100% transmission, with the distribution of the transmitted modes determined simply by the overlap of the mode wave functions and interference.

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“…Whether a defect potential acts as an obstacle or a sink, a wave-packet will interfere with, and possibly lose atoms as it goes through the defect due to the non-linearity [19,20], changing the interaction for any subsequent atom. In general, propagation through a perturbation in a 1-D waveguide results in unwanted transverse excitations of the BEC [8,21].…”

Section: Introductionmentioning

confidence: 99%

Scaling laws for the non-linear coupling constant of a Bose-Einstein condensate at the threshold of delocalization

Cabrera-Trujillo,

Bromley,

Esry

2012

Preprint

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We explore the localization of a quasi-one-, quasi-two-, and three-dimensional ultra-cold gas by a finite-range defect along the corresponding 'free'-direction/s. The time-independent non-linear Schrödinger equation that describes a Bose-Einstein condensate was used to calculate the maximum non-linear coupling constant, gmax, and thus the maximum number of atoms, Nmax, that the defect potential can localize. An analytical model, based on the Thomas-Fermi approximation, is introduced for the wavefunction. We show that gmax becomes a function of R0 √ V0 for various one-, two-, and three-dimensional defect shapes with depths V0 and characteristic lengths R0. Our explicit calculations show surprising agreement with this crude model over a wide range of V0 and R0. A scaling rule is also found for the wavefunction for the ground state at the threshold at which the localized states approach delocalization. The implication is that two defects with the same product R0 √ V0 will thus be related to each other with the same gmax and will have the same (reduced) density profile in the free-direction/s.

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Manifestations of vortices during ultracold-atom propagation through waveguides

Cited by 6 publications

References 29 publications

A straight quantum wave guide with mixed Dirichlet and Neumann boundary conditions in uniform magnetic fields

A straight quantum wave guide with mixed Dirichlet and Neumann boundary conditions in uniform magnetic fields

Transverse excitations of ultracold matter waves upon propagation past abrupt waveguide changes

Scaling laws for the non-linear coupling constant of a Bose-Einstein condensate at the threshold of delocalization

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