Yazar "Reimann, S. M." seçeneğine göre listele

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    Density-Functional Theory for Strongly Correlated Bosonic and Fermionic Ultracold Dipolar and Ionic Gases
    (AMER PHYSICAL SOC, 2015) Malet, F.; Mirtschink, A.; Mendl, C. B.; Bjerlin, J.; Karabulut, E. O.; Reimann, S. M.; Gori-Giorgi, Paola
    We introduce a density functional formalism to study the ground-state properties of strongly correlated dipolar and ionic ultracold bosonic and fermionic gases, based on the self-consistent combination of the weak and the strong coupling limits. Contrary to conventional density functional approaches, our formalism does not require a previous calculation of the interacting homogeneous gas, and it is thus very suitable to treat systems with tunable long-range interactions. Because of its asymptotic exactness in the regime of strong correlation, the formalism works for systems in which standard mean-field theories fail.
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    Finite-size effects in the dynamics of few bosons in a ring potential
    (IOP PUBLISHING LTD, 2018) Eriksson, G.; Bengtsson, J.; Karabulut, E. O.; Kavoulakis, G. M.; Reimann, S. M.
    We study the temporal evolution of a small number N of ultra-cold bosonic atoms confined in a ring potential. Assuming that initially the system is in a solitary-wave solution of the corresponding mean-field problem, we identify significant differences in the time evolution of the density distribution of the atoms when it instead is evaluated with the many-body Schrodinger equation. Three characteristic timescales are derived: the first is the period of rotation of the wave around the ring, the second is associated with a 'decay' of the density variation, and the third is associated with periodic 'collapses' and 'revivals' of the density variations, with a factor of root N separating each of them. The last two timescales tend to infinity in the appropriate limit of large N, in agreement with the mean-field approximation. These findings are based on the assumption of the initial state being a mean-field state. We confirm this behavior by comparison to the exact solutions for a few-body system stirred by an external potential. We find that the exact solutions of the driven system exhibit similar dynamical features.
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    Phase diagram of a rapidly rotating two-component Bose gas
    (AMER PHYSICAL SOC, 2013) Karabulut, E. O.; Malet, F.; Kavoulakis, G. M.; Reimann, S. M.
    We derive analytically the phase diagram of a two-component Bose gas confined in an anharmonic potential, which becomes exact and universal in the limit of weak interactions and small anharmonicity of the trapping potential. The transitions between the different phases, which consist of vortex states of single and multiple quantization, are all continuous because of the addition of the second component. DOI: 10.1103/PhysRevA.87.043609
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    Rotating Bose-Einstein condensates: Closing the gap between exact and mean-field solutions
    (AMER PHYSICAL SOC, 2015) Cremon, J. C.; Jackson, A. D.; Karabulut, E. O.; Kavoulakis, G. M.; Mottelson, B. R.; Reimann, S. M.
    When a Bose-Einstein-condensed cloud of atoms is given some angular momentum, it forms vortices arranged in structures with a discrete rotational symmetry. For these vortex states, the Hilbert space of the exact solution separates into a "primary" space related to the mean-field Gross-Pitaevskii solution and a "complementary" space including the corrections beyond mean field. Considering a weakly interacting Bose-Einstein condensate of harmonically trapped atoms, we demonstrate how this separation can be used to close the conceptual gap between exact solutions for systems with only a few atoms and the thermodynamic limit for which the mean field is the correct leading-order approximation. Although we illustrate this approach for the case of weak interactions, it is expected to be more generally valid.
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    Rotational properties of nondipolar and dipolar Bose-Einstein condensates confined in annular potentials
    (AMER PHYSICAL SOC, 2013) Karabulut, E. O.; Malet, F.; Kavoulakis, G. M.; Reimann, S. M.
    We investigate the rotational response of both nondipolar and dipolar Bose-Einstein condensates confined in an annular potential via minimization of the energy in the rotating frame. For the nondipolar case we identify certain phases which are associated with different vortex configurations. For the dipolar case, assuming that the dipoles are aligned along some arbitrary and tunable direction, we study the same problem as a function of the orientation angle of the dipole moment of the atoms. DOI: 10.1103/PhysRevA.87.033615
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    Spin-orbit-coupled Bose-Einstein-condensed atoms confined in annular potentials
    (IOP PUBLISHING LTD, 2016) Karabulut, E. O.; Malet, F.; Fetter, A. L.; Kavoulakis, G. M.; Reimann, S. M.
    A spin-orbit-coupled Bose-Einstein-condensed cloud of atoms confined in an annular trapping potential shows a variety of phases that we investigate in the present study. Starting with the non-interacting problem, the homogeneous phase that is present in an untrapped system is replaced by a sinusoidal density variation in the limit of a very narrow annulus. In the case of an untrapped system there is another phase with a striped-like density distribution, and its counterpart is also found in the limit of a very narrow annulus. As the width of the annulus increases, this picture persists qualitatively. Depending on the relative strength between the inter- and the intra-components, interactions either favor the striped phase, or suppress it, in which case either a homogeneous, or a sinusoidal-like phase appears. Interactions also give rise to novel solutions with a nonzero circulation.
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    Wigner-localized states in spin-orbit-coupled bosonic ultracold atoms with dipolar interaction
    (SPRINGER HEIDELBERG, 2015) Yousefi, Y.; Karabulut, E. O.; Malet, F.; Cremon, J.; Reimann, S. M.
    We investigate the occurence of Wigner-localization phenomena in bosonic dipolar ultracold few-body systems with Rashba-like spin-orbit coupling. We show that the latter strongly enhances the effects of the dipole-dipole interactions, allowing to reach the Wigner-localized regime for strengths of the dipole moment much smaller than those necessary in the spin-orbit-free case.