Browsing by Subject "Bosons"

Now showing 1 - 4 of 4

Open Access
Counterflow in Bose gas bilayers: collective modes and dissipationless drag
(American Institute of Physics, 2020) Abedinpour, S. H.; Tanatar, Bilal
We investigate the collective density oscillations and dissipationless drag effect in bilayer structures of ultra-cold bosons in the presence of counterflow. We consider different types of inter-particle interactions and obtain the drag coefficient and effect of counterflow on the sound velocity. We observe that counterflow enhances (suppresses) the energy of symmetric (asymmetric) density mode and drives the homogeneous system towards instability. The dependence of the drag coefficient on the spacing between two layers is determined by the form of particle-particle interaction.
Open Access
Dimensional crossover in two-dimensional Bose-Fermi mixtures
(Institute of Physics Publishing, 2010) Subaşi, A. L.; Sevinçli, S.; Vignolo, P.; Tanatar, Bilal
We 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.
Open Access
Phase boundary of the boson Mott insulator in a rotating optical lattice
(The American Physical Society, 2007) Umucalilar, R. O.; Oktel, M. Ö.
We consider the Bose-Hubbard model in a two-dimensional rotating optical lattice and investigate the consequences of the effective magnetic field created by rotation. Using a Gutzwiller-type variational wave function, we find an analytical expression for the Mott insulator (MI)-superfluid (SF) transition boundary in terms of the maximum eigenvalue of the Hofstadter butterfly. The dependence of phase boundary on the effective magnetic field is complex, reflecting the self-similar properties of the single particle energy spectrum. Finally, we argue that fractional quantum Hall phases exist close to the MI-SF transition boundaries, including MI states with particle densities greater than one.
Open Access
Two-dimensional boson-fermion mixtures
(2009) Subaşi, A.L.; Sevinçli, S.; Vignolo P.; Tanatar, Bilal
Using mean-field theory, we study the equilibrium properties of boson-fermion mixtures confined in a harmonic pancake-shaped trap at zero temperature. When the modulus of the s -wave scattering lengths are comparable to the mixture thickness, two-dimensional scattering events introduce a logarithmic dependence on density in the coupling constants, greatly modifying the density profiles themselves. We show that, for the case of a negative boson-fermion three-dimensional s -wave scattering length, the dimensional crossover stabilizes the mixture against collapse and drives it toward spatial demixing. © 2009 The American Physical Society.