1,466 research outputs found
Superfluid-Mott Insulator Transition of Spin-1 Bosons in an Optical Lattice
We have studied superfluid-Mott insulating transition of spin-1 bosons
interacting antiferromagnetically in an optical lattice. We have obtained the
zero-temperature phase diagram by a mean-field approximation and have found
that the superfluid phase is to be a polar state as a usual trapped spin-1 Bose
gas. More interestingly, we have found that the Mott-insulating phase is
strongly stabilized only when the number of atoms per site is even.Comment: 9 pages, 1 figur
Bose-Einstein condensation at constant temperature
We present a novel experimental approach to Bose-Einstein condensation by
increasing the particle number of the system at almost constant temperature. In
particular the emergence of a new condensate is observed in multi-component F=1
spinor condensates of 87-Rb. Furthermore we develop a simple rate-equation
model for multi-component BEC thermodynamics at finite temperature which well
reproduces the measured effects.Comment: 4 pages, 3 figures, RevTe
Ultra-precise measurement of optical frequency ratios
We developed a novel technique for frequency measurement and synthesis, based
on the operation of a femtosecond comb generator as transfer oscillator. The
technique can be used to measure frequency ratios of any optical signals
throughout the visible and near-infrared part of the spectrum. Relative
uncertainties of for averaging times of 100 s are possible. Using a
Nd:YAG laser in combination with a nonlinear crystal we measured the frequency
ratio of the second harmonic at 532 nm to the fundamental at
1064 nm, .Comment: 4 pages, 4 figure
Static properties and spin dynamics of the ferromagnetic spin-1 Bose gas in magnetic field
Properties of spin-1 Bose gases with ferromagnetic interaction in the
presence of a nonzero magnetic field are studied. The equation of state and
thermodynamic quantities are worked out with the help of a mean-field
approximation. The phase diagram besides Bose-Einstein condensation contains a
first order transition where two values of the magnetization coexist. The
dynamics is investigated with the help of the Random Phase Approximation. The
soft mode corresponding to the critical point of the magnetic phase transition
is found to behave like in conventional theory.Comment: 8 pages and 3 figures included in text, submitted to Physical Review
Vortex structure in spinor F=2 Bose-Einstein condensates
Extended Gross-Pitaevskii equations for the rotating F=2 condensate in a
harmonic trap are solved both numerically and variationally using trial
functions for each component of the wave function. Axially-symmetric vortex
solutions are analyzed and energies of polar and cyclic states are calculated.
The equilibrium transitions between different phases with changing of the
magnetization are studied. We show that at high magnetization the ground state
of the system is determined by interaction in "density" channel, and at low
magnetization spin interactions play a dominant role. Although there are five
hyperfine states, all the particles are always condensed in one, two or three
states. Two novel types of vortex structures are also discussed.Comment: 6 pages, 3 figure
A laser-driven target of high-density nuclear polarized hydrogen gas
We report the best figure-of-merit achieved for an internal nuclear polarized
hydrogen gas target and a Monte Carlo simulation of spin-exchange optical
pumping. The dimensions of the apparatus were optimized using the simulation
and the experimental results were in good agreement with the simulation. The
best result achieved for this target was 50.5% polarization with 58.2% degree
of dissociation of the sample beam exiting the storage cell at a hydrogen flow
rate of atoms/s.Comment: Accepted as a Rapid Communication article in Phys. Rev.
Momentum interferences of a freely expanding Bose-Einstein condensate in 1D due to interatomic interaction change
A Bose-Einstein condensate may be prepared in a highly elongated harmonic
trap with negligible interatomic interactions using a Feshbach resonance. If a
strong repulsive interatomic interaction is switched on and the axial trap is
removed to let the condensate evolve freely in the axial direction, a time
dependent quantum interference pattern takes place in the short time
(Thomas-Fermi) regime, in which the number of peaks of the momentum
distribution increases one by one, whereas the spatial density barely changes.Comment: 4 pages, 5 figure
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