6,036 research outputs found
Rayleigh scattering and atomic dynamics in dissipative optical lattices
We investigate Rayleigh scattering in dissipative optical lattices. In particular, following recent proposals [S. Guibal et al., Phys. Rev. Lett. 78, 4709 (1997); C. Jurczak et al., Phys. Rev. Lett. 77, 1727 (1996)], we study whether the Rayleigh resonance originates from the diffraction on a density grating and is therefore a probe of transport of atoms in optical lattices. It turns out that this is not the case: the Rayleigh line is instead a measure of the cooling rate, while spatial diffusion contributes to the scattering spectrum with a much broader resonance
Phase-control of directed diffusion in a symmetric optical lattice
We demonstrate the phenomenon of directed diffusion in a symmetric periodic
potential. This has been realized with cold atoms in a one-dimensional
dissipative optical lattice. The stochastic process of optical pumping leads to
a diffusive dynamics of the atoms through the periodic structure, while a
zero-mean force which breaks the temporal symmetry of the system is applied by
phase-modulating one of the lattice beams. The atoms are set into directed
motion as a result of the breaking of the temporal symmetry of the system
Stochastic resonance in periodic potentials: realization in a dissipative optical lattice
We have observed the phenomenon of stochastic resonance on the Brillouin
propagation modes of a dissipative optical lattice. Such a mode has been
excited by applying a moving potential modulation with phase velocity equal to
the velocity of the mode. Its amplitude has been characterized by the
center-of-mass (CM) velocity of the atomic cloud. At Brillouin resonance, we
studied the CM-velocity as a function of the optical pumping rate at a given
depth of the potential wells. We have observed a resonant dependence of the CM
velocity on the optical pumping rate, corresponding to the noise strength. This
corresponds to the experimental observation of stochastic resonance in a
periodic potential in the low-damping regime
Localized and extended states in a disordered trap
We study Anderson localization in a disordered potential combined with an
inhomogeneous trap. We show that the spectrum displays both localized and
extended states, which coexist at intermediate energies. In the region of
coexistence, we find that the extended states result from confinement by the
trap and are weakly affected by the disorder. Conversely, the localized states
correspond to eigenstates of the disordered potential, which are only affected
by the trap via an inhomogeneous energy shift. These results are relevant to
disordered quantum gases and we propose a realistic scheme to observe the
coexistence of localized and extended states in these systems.Comment: Published versio
A model of dispersive transport across sharp interfaces between porous materials
Recent laboratory experiments on solute migration in composite porous columns
have shown an asymmetry in the solute arrival time upon reversal of the flow
direction, which is not explained by current paradigms of transport. In this
work, we propose a definition for the solute flux across sharp interfaces and
explore the underlying microscopic particle dynamics by applying Monte Carlo
simulation. Our results are consistent with previous experimental findings and
explain the observed transport asymmetry. An interpretation of the proposed
physical mechanism in terms of a flux rectification is also provided. The
approach is quite general and can be extended to other situations involving
transport across sharp interfaces.Comment: 4 pages, 4 figure
Bose-Einstein Condensates in Optical Quasicrystal Lattices
We analyze the physics of Bose-Einstein condensates confined in 2D
quasi-periodic optical lattices, which offer an intermediate situation between
ordered and disordered systems. First, we analyze the time-of-flight
interference pattern that reveals quasi-periodic long-range order. Second, we
demonstrate localization effects associated with quasi-disorder as well as
quasiperiodic Bloch oscillations associated with the extended nature of the
wavefunction of a Bose-Einstein condensate in an optical quasicrystal. In
addition, we discuss in detail the crossover between diffusive and localized
regimes when the quasi-periodic potential is switched on, as well as the
effects of interactions
Inhibition of Transport of a Bose-Einstein Condensate in a Random Potential
We observe the suppression of the 1D transport of an interacting elongated
Bose-Einstein condensate in a random potential with a standard deviation small
compared to the typical energy per atom, dominated by the interaction energy.
Numerical solutions of the Gross-Pitaevskii equation reproduce well our
observations. We propose a scenario for disorder-induced trapping of the
condensate in agreement with our observations.Comment: Proceedings of the 17th International Conference on Laser
Spectroscopy (ICOLS 05), Cairngorms National Park, Scotland, 19-24 June 200
Temperature and spatial diffusion of atoms cooled in a 3D linlin bright optical lattice
We present a detailed experimental study of a three-dimensional linlin
bright optical lattice. Measurements of the atomic temperature and spatial
diffusion coefficients are reported for different angles between the lattice
beams, i.e. for different lattice constants. The experimental findings are
interpretated with the help of numerical simulations. In particular we show,
both experimentally and theoretically, that the temperature is independent of
the lattice constant.Comment: accepted for publication in Eur. Phys. J.
Localization of solitons: linear response of the mean-field ground state to weak external potentials
Two aspects of bright matter-wave solitons in weak external potentials are
discussed. First, we briefly review recent results on the Anderson localization
of an entire soliton in disordered potentials [Sacha et al. PRL 103, 210402
(2009)], as a paradigmatic showcase of genuine quantum dynamics beyond simple
perturbation theory. Second, we calculate the linear response of the mean-field
soliton shape to a weak, but otherwise arbitrary external potential, with a
detailed application to lattice potentials.Comment: Selected paper presented at the 2010 Spring Meeting of the Quantum
Optics and Photonics Section of the German Physical Society. V2: minor
changes, published versio
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