Browsing by Author "Vignolo, P."
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Item Open Access Density profile of a Bose-Einstein condensate inside a pancake-shaped trap: Observational consequences of the dimensional cross-over in the scattering properties(Elsevier Science B.V., 2002) Tanatar, Bilal; Minguzzi, A.; Vignolo, P.; Tosi, M. P.It is theoretically well known that two-dimensionality of the scattering events in a Bose-Einstein condensate introduces a logarithmic dependence on density in the coupling constant entering a mean-field theory of the equilibrium density profile, which becomes dominant as the s-wave scattering length gets larger than the condensate thickness. We trace the regions of experimentally accessible system parameters for which the cross-over between different dimensionality behaviors in the scattering properties may become observable through in situ imaging of the condensed cloud with varying trap anisotropy and scattering length.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 Metal-insulator transition induced by random dipoles(American Physical Society, 2013) Larcher, M.; Menotti, C.; Tanatar, Bilal; Vignolo, P.We study the localization properties of a test dipole feeling the disordered potential induced by dipolar impurities trapped at random positions in an optical lattice. This random potential is marked by correlations which are a convolution of short-range and long-range ones. We show that when short-range correlations are dominant, extended states can appear in the spectrum. Introducing long-range correlations, the extended states, if any, are wiped out and localization is restored over the whole spectrum. Moreover, long-range correlations can either increase or decrease the localization length at the center of the band, which indicates a richer behavior than previously predicted.Item Open Access Temperature dependence of the energy of a vortex in a two-dimensional Bose gas(Elsevier, 2004) Rajagopal, K. K.; Tanatar, Bilal; Vignolo, P.; Tosi, M. P.We evaluate the thermodynamic critical angular velocity Ωc(T) for creation of a vortex of lowest quantized angular momentum in a strictly two-dimensional Bose gas at temperature T, using a mean-field two-fluid model for the condensate and the thermal cloud. Our results show that (i) a Thomas-Fermi description of the condensate badly fails in predicting the particle density profiles and the energy of the vortex as functions of T; and (ii) an extrapolation of a simple Thomas-Fermi formula for Ωc(0) is nevertheless approximately useful up to T≃0.5Tc.