351 research outputs found
Boson-fermion mixtures inside an elongated cigar-shaped trap
We present mean-field calculations of the equilibrium state in a gaseous
mixture of bosonic and spin-polarized fermionic atoms with repulsive or
attractive interspecies interactions, confined inside a cigar-shaped trap under
conditions such that the radial thickness of the two atomic clouds is
approaching the magnitude of the s-wave scattering lengths. In this regime the
kinetic pressure of the fermionic component is dominant. Full demixing under
repulsive boson-fermion interactions can occur only when the number of fermions
in the trap is below a threshold, and collapse under attractive interactions is
suppressed within the range of validity of the mean-field model. Specific
numerical illustrations are given for values of system parameters obtaining in
7Li-6Li clouds.Comment: 12 pages, 6 figure
Sound propagation in elongated superfluid fermion clouds
We use hydrodynamic equations to study sound propagation in a superfluid
Fermi gas inside a strongly elongated cigar-shaped trap, with main attention to
the transition from the BCS to the unitary regime. We treat first the role of
the radial density profile in the quasi-onedimensional limit and then evaluate
numerically the effect of the axial confinement in a configuration in which a
hole is present in the gas density at the center of the trap. We find that in a
strongly elongated trap the speed of sound in both the BCS and the unitary
regime differs by a factor sqrt{3/5} from that in a homogeneous
three-dimensional superfluid. The predictions of the theory could be tested by
measurements of sound-wave propagation in a set-up such as that exploited by
M.R. Andrews et al. [Phys. Rev. Lett. 79, 553 (1997)] for an atomic
Bose-Einstein condensate
Faraday waves in elongated superfluid fermionic clouds
We use hydrodynamic equations to study the formation of Faraday waves in a
superfluid Fermi gas at zero temperature confined in a strongly elongated
cigar-shaped trap. First, we treat the role of the radial density profile in
the limit of an infinite cylindrical geometry and analytically evaluate the
wavelength of the Faraday pattern. The effect of the axial confinement is fully
taken into account in the numerical solution of hydrodynamic equations and
shows that the infinite cylinder geometry provides a very good description of
the phenomena.Comment: 6 pages, 7 figures. Figures 4 and 6 in high resolution on reques
Matter-wave interferometry in periodic and quasi-periodic arrays
We calculate within a Bose-Hubbard tight-binding model the matter-wave flow
driven by a constant force through a Bose-Einstein condensate of Rb 87 atoms in
various types of quasi-onedimensional arrays of potential wells. Interference
patterns are obtained when beam splitting is induced by creating energy
minigaps either through period doubling or through quasi-periodicity governed
by the Fibonacci series. The generation of such condensate modulations by means
of optical-laser structures is also discussed.Comment: 11 pages, 6 figures. To appear in Opt. Com
Shell structure in the density profile of a rotating gas of spin-polarized fermions
We present analytical expressions and numerical illustrations for the
ground-state density distribution of an ideal gas of spin-polarized fermions
moving in two dimensions and driven to rotate in a harmonic well of circular or
elliptical shape. We show that with suitable choices of the strength of the
Lorentz force for charged fermions, or of the rotational frequency for neutral
fermions, the density of states can be tuned as a function of the angular
momentum so as to display a prominent shell structure in the spatial density
profile of the gas. We also show how this feature of the density profile is
revealed in the static structure factor determining the elastic light
scattering spectrum of the gas.Comment: 12 pages, 6 figure
Transition to hydrodynamics in colliding fermion clouds
We study the transition from the collisionless to the hydrodynamic regime in
a two-component spin-polarized mixture of 40K atoms by exciting its dipolar
oscillation modes inside harmonic traps. The time evolution of the mixture is
described by the Vlasov-Landau equations and numerically solved with a fully
three-dimensional concurrent code. We observe a master/slave behaviour of the
oscillation frequencies depending on the dipolar mode that is excited.
Regardless of the initial conditions, the transition to hydrodynamics is found
to shift to lower values of the collision rate as temperature decreases.Comment: 11 pages, iop style. submitted to the proceedings of the Levico 2003
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