Browsing by Subject "Gas condensates"
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Item Open Access Dimensional crossover in two-dimensional Bose-Fermi mixtures(Institute of Physics Publishing, 2010) Subaşi, A. L.; Sevinçli, S.; Vignolo, P.; Tanatar, BilalWe investigate the equilibrium properties of boson-fermion mixtures consisting of a Bose condensate and spin-polarized Fermi gas confined in a harmonic two-dimensional (2D) trap using mean-field theory. Boson-boson and boson-fermion coupling constants have a logarithmic dependence on the density because of the two-dimensional scattering events when the s-wave scattering lengths are on the order of mixture thickness. We show that this modifies the density profiles significantly. It is also shown that the dimensional crossover stabilizes the mixture against collapse and spatial demixing is observed for the case of a negative boson-fermion scattering length.Item Open Access Free expansion of two-dimensional condensates with a vortex(Institute of Physics Publishing, 2003) Hoşten, O.; Vignolo, P.; Minguzzi, A.; Tanatar, Bilal; Tosi, M. P.We study the free expansion of a pancake-shaped Bose-condensed gas, which is initially trapped under harmonic confinement and containing a vortex at its centre. In the case of a radial expansion holding the axial confinement fixed we consider various models for the interactions, depending on the thickness of the condensate relative to the value of the scattering length. We are thus able to evaluate different scattering regimes ranging from quasi-three-dimensional (Q3D) to strictly two-dimensional (2D). We find that as the system goes from Q3D to 2D the expansion rate of the condensate increases whereas that of the vortex core decreases. In the Q3D scattering regime we also examine a fully free expansion in 3D and find oscillatory behaviour for the vortex core radius: an initial fast expansion of the vortex core is followed by a slowing down. Such a nonuniform expansion rate of the vortex core implies that the timing of its observation should be chosen appropriately.Item Open Access The ground state and vortices in a two-dimensional Bose gas confined in a harmonic trap(Institute of Physics Publishing, 2002) Tanatar, BilalWe study the ground state properties of a two-dimensional Bose gas in an harmonic trap potential using the recently proposed mean-field equation that takes into account the correct dimensionality effect. In contrast to the threedimensional case, the interaction term depends logarithmically on the scattering length and density. We compare our results with other approaches with various forms for the two-dimensional coupling. We also consider the vortex states and study the effects of density-dependent interactions on the formation of vortices.Item Open Access Vortex lattice of a Bose-Einstein condensate in a rotating anisotropic trap(American Physical Society, 2004) Oktel, M. Ö.The behavior of Bose-Einstein condensates (BEC) with a vortex lattice in a rotating anisotropic trap was studied. The single-particle wave functions for a rotating anisotropy trap were found by exactly diagonalizing the Hamiltonian. The wave functions in the lowest Landau level (LLL) were shown to be written as simple analytic functions in the small anisotropy limit. The results show that the regularity of the vortex configurations observed in an axisymmetric trap is disturbed by the anisotropy of the confinement.