15 research outputs found
Vortex patterns in a fast rotating Bose-Einstein condensate
For a fast rotating condensate in a harmonic trap, we investigate the
structure of the vortex lattice using wave functions minimizing the Gross
Pitaveskii energy in the Lowest Landau Level. We find that the minimizer of the
energy in the rotating frame has a distorted vortex lattice for which we plot
the typical distribution. We compute analytically the energy of an infinite
regular lattice and of a class of distorted lattices. We find the optimal
distortion and relate it to the decay of the wave function. Finally, we
generalize our method to other trapping potentials
The atomic Bose gas in Flatland
We describe a recent experiment performed with rubidium atoms (Rb),
aiming at studying the coherence properties of a two-dimensional gas of bosonic
particles at low temperature. We have observed in particular a
Berezinskii--Kosterlitz--Thouless (BKT) type crossover in the system, using a
matter wave heterodyning technique. At low temperatures, the gas is
quasi-coherent on the length scale set by the system size. As the temperature
is increased, the loss of long-range coherence coincides with the onset of the
proliferation of free vortices, in agreement with the microscopic BKT theory.Comment: To appear in "ATOMIC PHYSICS 20" Proceedings of the XX International
Conference on Atomic Physics (ICAP
Seeing zeros of random polynomials: quantized vortices in the ideal Bose gas
We propose a physical system allowing one to experimentally observe the
distribution of the complex zeros of a random polynomial. We consider a
degenerate, rotating, quasi-ideal atomic Bose gas prepared in the lowest Landau
level. Thermal fluctuations provide the randomness of the bosonic field and of
the locations of the vortex cores. These vortices can be mapped to zeros of
random polynomials, and observed in the density profile of the gas.Comment: 4 page
Collective oscillations of a classical gas confined in harmonic traps
Starting from the Boltzmann equation we calculate the frequency and the
damping of the monopole and quadrupole oscillations of a classical gas confined
in an harmonic potential. The collisional term is treated in the relaxation
time approximation and a gaussian ansatz is used for its evaluation. Our
approach provides an explicit description of the transition between the
hydrodynamic and collisionless regimes in both spherical and deformed traps.
The predictions are compared with the results of a numerical simulation.Comment: 6 pages, revtex, 2 figures include
Quantum Hall states for in optical lattices
We examine the quantum Hall (QH) states of the optical lattices with square
geometry using Bose-Hubbard model (BHM) in presence of artificial gauge field.
In particular, we focus on the QH states for the flux value of .
For this, we use cluster Gutzwiller mean-field (CGMF) theory with cluster sizes
of and . We obtain QH states at fillings with the cluster size and with cluster. Our results show that the geometry
of the QH states are sensitive to the cluster sizes. For all the values of
, the competing superfluid (SF) state is the ground state and QH state is
the metastable state.Comment: 6 pages, 4 figures. This is a pre-submission version of the
manuscript. The published version is available online in "Quantum Collisions
and Confinement of Atomic and Molecular Species, and Photons, Springer
Proceedings in Physics 230, pp 211--221 (2019)". The final authenticated
version is available online at : https://doi.org/10.1007/978-981-13-9969-5_2
Many-Body Physics with Ultracold Gases
This article reviews recent experimental and theoretical progress on
many-body phenomena in dilute, ultracold gases. Its focus are effects beyond
standard weak-coupling descriptions, like the Mott-Hubbard-transition in
optical lattices, strongly interacting gases in one and two dimensions or
lowest Landau level physics in quasi two-dimensional gases in fast rotation.
Strong correlations in fermionic gases are discussed in optical lattices or
near Feshbach resonances in the BCS-BEC crossover.Comment: revised version, accepted for publication in Rev. Mod. Phy