168 research outputs found
Production of ultracold heteronuclear YbRb* molecules by photoassociation
We have produced ultracold heteronuclear YbRb molecules in a combined
magneto-optical trap by photoassociation. The formation of electronically
excited molecules close to the dissociation limit was observed by trap loss
spectroscopy in mixtures of Rb with Yb and Yb. The
molecules could be prepared in a series of vibrational levels with resolved
rotational structure, allowing for an experimental determination of the
long-range potential in the electronically excited state
Spatial separation in a thermal mixture of ultracold Yb and Rb atoms
We report on the observation of unusually strong interactions in a thermal
mixture of ultracold atoms which cause a significant modification of the
spatial distribution. A mixture of Rb and Yb with a temperature
of a few K is prepared in a hybrid trap consisting of a bichromatic
optical potential superimposed on a magnetic trap. For suitable trap parameters
and temperatures, a spatial separation of the two species is observed. We infer
that the separation is driven by a large interaction strength between
Yb and Rb accompanied by a large three-body recombination rate.
Based on this assumption we have developed a diffusion model which reproduces
our observations
Sympathetic cooling in a mixture of diamagnetic and paramagnetic atoms
We have experimentally realized a hybrid trap for ultracold paramagnetic
rubidium and diamagnetic ytterbium atoms by combining a bichromatic optical
dipole trap for ytterbium with a Ioffe-Pritchard-type magnetic trap for
rubidium. In this hybrid trap, sympathetic cooling of five different ytterbium
isotopes through elastic collisions with rubidium was achieved. A strong
dependence of the interspecies collisional cross section on the mass of the
ytterbium isotope was observed.Comment: 4 pages, 4 figure
Controlled Generation of Dark Solitons with Phase Imprinting
The generation of dark solitons in Bose-Einstein condensates with phase
imprinting is studied by mapping it into the classic problem of a damped driven
pendulum. We provide simple but powerful schemes of designing the phase imprint
for various desired outcomes. We derive a formula for the number of dark
solitons generated by a given phase step, and also obtain results which explain
experimental observations.Comment: 4pages, 4 figure
Strong spin-orbit induced Gilbert damping and g-shift in iron-platinum nanoparticles
The shape of ferromagnetic resonance spectra of highly dispersed, chemically
disordered Fe_{0.2}Pt_{0.8} nanospheres is perfectly described by the solution
of the Landau-Lifshitz-Gilbert (LLG) equation excluding effects by crystalline
anisotropy and superparamagnetic fluctuations. Upon decreasing temperature, the
LLG damping and a negative g-shift, g(T)-g_0, increase proportional
to the particle magnetic moments determined from the Langevin analysis of the
magnetization isotherms. These novel features are explained by the scattering
of the magnon from an electron-hole (e/h) pair mediated by the
spin-orbit coupling, while the sd-exchange can be ruled out. The large
saturation values, and , indicate the
dominance of an overdamped 1 meV e/h-pair which seems to originate from the
discrete levels of the itinerant electrons in the d_p=3 nm nanoparticles.Comment: 8 pages, 4 figures, accepted for publication in Phys. Rev. B
(http://prb.aps.org/
Statistical Properties of Interacting Bose Gases in Quasi-2D Harmonic Traps
The analytical probability distribution of the quasi-2D (and purely 2D) ideal
and interacting Bose gas are investigated by using a canonical ensemble
approach. Using the analytical probability distribution of the condensate, the
statistical properties such as the mean occupation number and particle number
fluctuations of the condensate are calculated. Researches show that there is a
continuous crossover of the statistical properties from a quasi-2D to a purely
2D ideal or interacting gases. Different from the case of a 3D Bose gas, the
interaction between atoms changes in a deep way the nature of the particle
number fluctuations.Comment: RevTex, 10pages, 4 figures, E-mail: [email protected]
Split vortices in optically coupled Bose-Einstein condensates
We study a rotating two-component Bose-Einstein condensate in which an
optically induced Josephson coupling allows for population transfer between the
two species. In a regime where separation of species is favored, the ground
state of the rotating system displays domain walls with velocity fields normal
to them. Such a configuration looks like a vortex split into two halves, with
atoms circulating around the vortex and changing their internal state in a
continuous way.Comment: 4 EPS pictures, 4 pages; Some errata have been corrected and thep
resentation has been slightly revise
Anisotropic Bose-Einstein condensates and completely integrable dynamical systems
A Gaussian ansatz for the wave function of two-dimensional harmonically
trapped anisotropic Bose-Einstein condensates is shown to lead, via a
variational procedure, to a coupled system of two second-order, nonlinear
ordinary differential equations. This dynamical system is shown to be in the
general class of Ermakov systems. Complete integrability of the resulting
Ermakov system is proven. Using the exact solution, collapse of the condensate
is analyzed in detail. Time-dependence of the trapping potential is allowed
Hydrodynamic modes of a 1D trapped Bose gas
We consider two regimes where a trapped Bose gas behaves as a one-dimensional
system. In the first one the Bose gas is microscopically described by 3D mean
field theory, but the trap is so elongated that it behaves as a 1D gas with
respect to low frequency collective modes. In the second regime we assume that
the 1D gas is truly 1D and that it is properly described by the Lieb-Liniger
model. In both regimes we find the frequency of the lowest compressional mode
by solving the hydrodynamic equations. This is done by making use of a method
which allows to find analytical or quasi-analytical solutions of these
equations for a large class of models approaching very closely the actual
equation of state of the Bose gas. We find an excellent agreement with the
recent results of Menotti and Stringari obtained from a sum rule approach.Comment: 15 pages, revtex, 1 figure
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