| 1. |
- Bergkvist, Sara, et al.
(författare)
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Transition from a two-dimensional superfluid to a one-dimensional mott insulator
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:11, s. 110401-1-110401-5
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Tidskriftsartikel (refereegranskat)abstract
- A two-dimensional system of atoms in an anisotropic optical lattice is studied theoretically. If the system is finite in one direction, it is shown to exhibit a transition between a two-dimensional superfluid and a one-dimensional Mott insulating chain of superfluid tubes. Monte Carlo simulations are consistent with the expectation that the phase transition is of Kosterlitz-Thouless type. The effect of the transition on experimental time-of-flight images is discussed.
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| 2. |
- Rehn, Magnus, 1972-, et al.
(författare)
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One-dimensional phase transitions in a two-dimensional optical lattice
- 2008
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 49:2, s. 223-230
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Tidskriftsartikel (refereegranskat)abstract
- A phase transition for bosonic atoms in a two-dimensional anisotropic optical lattice is considered. If the tunnelling rates in two directions are different, the system can undergo a transition between a two-dimensional superfluid and a one-dimensional Mott insulating array of strongly coupled tubes. The connection to other lattice models is exploited in order to better understand the phase transition. Critical properties are obtained using quantum Monte Carlo calculations. These critical properties are related to correlation properties of the bosons and a criterion for commensurate filling is established.
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| 3. |
- Dion, Claude, 1970-, et al.
(författare)
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Bimodal momentum distribution of laser-cooled atoms in optical lattices
- 2016
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 93:5
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Tidskriftsartikel (refereegranskat)abstract
- We study, numerically and experimentally, the momentum distribution of atoms cooled in optical lattices. Using semiclassical simulations, we show that this distribution is bimodal, made up of a central feature corresponding to "cold," trapped atoms, with tails of "hot," untrapped atoms, and that this holds true also for very shallow potentials. Careful analysis of the distribution of high-momentum untrapped atoms, both from simulations and experiments, shows that the tails of the distribution do not follow a normal law, hinting at a power-law distribution and nonergodic behavior. We also revisit the phenomenon leading to the existence of an optimal cooling point, i.e., a potential depth below which the temperature of the atoms starts increasing.
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| 4. |
- Dion, Claude, et al.
(författare)
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Controllable 3D atomic Brownian motor in optical lattices
- 2008
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Ingår i: The European Physical Journal - Special Topics. - : Springer Science and Business Media LLC. - 1951-6355 .- 1951-6401. ; 159:1, s. 11-17
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Tidskriftsartikel (refereegranskat)abstract
- We study a Brownian motor, based on cold atoms in optical lattices, where atomic motion can be induced in a controlled manner in an arbitrary direction, by rectification of isotropic random fluctuations. In contrast with ratchet mechanisms, our Brownian motor operates in a potential that is spatially and temporally symmetric, in apparent contradiction to the Curie principle. Simulations, based on the Fokker-Planck equation, allow us to gain knowledge on the qualitative behaviour of our Brownian motor. Studies of Brownian motors, and in particular ones with unique control properties, are of fundamental interest because of the role they play in protein motors and their potential applications in nanotechnology. In particular, our system opens the way to the study of quantum Brownian motors.
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| 5. |
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| 6. |
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| 7. |
- Dion, Claude M., et al.
(författare)
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Time dependence of laser cooling in optical lattices
- 2005
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Ingår i: Europhysics letters. - Les Ulis : Éditions de physique. - 0295-5075 .- 1286-4854. ; 72:3, s. 369-375
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Tidskriftsartikel (refereegranskat)abstract
- We study the dynamics of the cooling of a gas of caesium atoms in an optical lattice, both experimentally and with 1D full-quantum Monte Carlo simulations. We find that, contrary to the standard interpretation of the Sisyphus model, the cooling process does not work by a continuous decrease of the average kinetic energy of the atoms in the lattice. Instead, we show that the momentum of the atoms follows a bimodal distribution, the atoms being gradually transferred from a hot to a cold mode. We suggest that the cooling mechanism should be depicted in terms of a rate model, describing the transfer between the two modes along with the processes occurring within each mode.
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| 8. |
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| 9. |
- Ellmann, Harald, et al.
(författare)
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Experiments with a 3D Double Optical Lattice
- 2003
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 90:5, s. 053001-
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Tidskriftsartikel (refereegranskat)abstract
- We present a setup where we trap two different cesium hyperfine ground states in two different near-resonant optical lattices with identical topographies. We demonstrate that we can change the relative spatial phase between the lattices and we measure the equilibrium temperature as a function of the relative spatial phase. This provides a topographical chart of the optical potential. We also determine the rate at which atoms are transferred between the lattices and show that the setup is a promising candidate for implementing coherent quantum state manipulation.
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| 10. |
- Ellmann, Harald, et al.
(författare)
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Experiments with a 3D double optical lattice
- 2003
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 90:5
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Tidskriftsartikel (refereegranskat)abstract
- We present a setup where we trap two different cesium hyperfine ground states in two different near-resonant optical lattices with identical topographies. We demonstrate that we can change the relative spatial phase between the lattices and we measure the equilibrium temperature as a function of the relative spatial phase. This provides a topographical chart of the optical potential. We also determine the rate at which atoms are transferred between the lattices and show that the setup is a promising candidate for implementing coherent quantum state manipulation.
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