1,723 research outputs found
Interaction-induced excited-band condensate in a double-well optical lattice
We show theoretically that interaction effects in a double-well optical
lattice can induce condensates in an excited band. For a symmetric double-well
lattice, bosons condense into the bottom of the excited band at the edge of the
Brillouin Zone if the chemical potential is above a critical value. For an
asymmetric lattice, a condensate with zero momentum is automatically induced in
the excited band by the condensate in the lowest band. This is due to a
combined effect of interaction and lattice potential, which reduces the band
gap and breaks the inversion symmetry. Our work can be generalized to a
superlattice composed of multiple-well potentials at each lattice site, where
condensates can be induced in even higher bands.Comment: 4pages, 3 figure
Quantum and Classical Dynamics of a BEC in a Large-Period Optical Lattice
We experimentally investigate diffraction of a Rb-87 Bose-Einstein condensate
from a 1D optical lattice. We use a range of lattice periods and timescales,
including those beyond the Raman-Nath limit. We compare the results to quantum
mechanical and classical simulations, with quantitative and qualitative
agreement, respectively. The classical simulation predicts that the envelope of
the time-evolving diffraction pattern is shaped by caustics: singularities in
the phase space density of classical trajectories. This behavior becomes
increasingly clear as the lattice period grows.Comment: 7 pages, 6 figure
Universal Behaviour of the Superfluid Fraction and Tc of He-3 in 99.5% Open Aerogel
We have investigated the superfluid transition of He-3 in a 99.5% porosity
silica aerogel. This very dilute sample shows behaviour intermediary between
bulk He-3 and He-3 confined to the denser aerogels previously studied. We
present data on both the superfluid transition temperature and the superfluid
density and compare our results with previous measurements. Finally, we show
that the suppression of the superfluid transition temperature and suppression
of the superfluid density of He-3 in aerogel follow a universal relation for a
range of aerogel samples.Comment: 4 pages, 5 figures; 1 new figure, minor change
Strongly inhibited transport of a 1D Bose gas in a lattice
We report the observation of strongly damped dipole oscillations of a quantum
degenerate 1D atomic Bose gas in a combined harmonic and optical lattice
potential. Damping is significant for very shallow axial lattices (0.25 photon
recoil energies), and increases dramatically with increasing lattice depth,
such that the gas becomes nearly immobile for times an order of magnitude
longer than the single-particle tunneling time. Surprisingly, we see no
broadening of the atomic quasimomentum distribution after damped motion. Recent
theoretical work suggests that quantum fluctuations can strongly damp dipole
oscillations of 1D atomic Bose gas, providing a possible explanation for our
observations.Comment: 5 pages, 4 figure
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