44,134 research outputs found
Ultracold dipolar gases - a challenge for experiments and theory
We present a review of recent results concerning the physics of ultracold
trapped dipolar gases. In particular, we discuss the Bose-Einstein condensation
for dipolar Bose gases and the BCS transition for dipolar Fermi gases. In both
cases we stress the dominant role of the trap geometry in determining the
properties of the system. We present also results concerning bosonic dipolar
gases in optical lattices and the possibility of obtaining variety of different
quantum phases in such case. Finally, we analyze various possible routes
towards achieving ultracold dipolar gases.Comment: This paper is based on the lecture given by M. Lewenstein at the
Nobel Symposium ''Coherence and Condensation in Quantum Systems'',
Gothesburg, 4-7.12.200
Disorderless quasi-localization of polar gases in one-dimensional lattices
One-dimensional polar gases in deep optical lattices present a severely
constrained dynamics due to the interplay between dipolar interactions, energy
conservation, and finite bandwidth. The appearance of dynamically-bound
nearest-neighbor dimers enhances the role of the dipolar tail,
resulting, in the absence of external disorder, in quasi-localization via dimer
clustering for very low densities and moderate dipole strengths. Furthermore,
even weak dipoles allow for the formation of self-bound superfluid lattice
droplets with a finite doping of mobile, but confined, holons. Our results,
which can be extrapolated to other power-law interactions, are directly
relevant for current and future lattice experiments with magnetic atoms and
polar molecules.Comment: 5 + 2 Page
Field-induced phase transitions of repulsive spin-1 bosons in optical lattices
We study the phase diagram of repulsively interacting spin-1 bosons in
optical lattices at unit filling, showing that an externally induced quadratic
Zeeman effect may lead to a rich physics characterized by various phases and
phase transitions. We find that the main properties of the system may be
described by an effective field model, which provides the precise location of
the phase boundaries for any dimension, being in excellent agreement with our
numerical calculations for one-dimensional systems. Our work provides a
quantitative guide for the experimental analysis of various types of
field-induced quantum phase transitions in spin-1 lattice bosons. These
transitions, which are precluded in spin-1/2 systems, may be realized using an
externally modified quadratic Zeeman coupling, similar to recent experiments
with spinor condensates in the continuum.Comment: 4 pages, 2 figure
Laser Cooling of Trapped Fermi Gases deeply below the Fermi Temperature
We study the collective Raman cooling of a polarized trapped Fermi gas in the
Festina Lente regime, when the heating effects associated with photon
reabsorptions are suppressed. We predict that by adjusting the spontaneous
Raman emission rates and using appropriately designed anharmonic traps,
temperatures of the order of 2.7% of the Fermi temperature can be achieved in
3D.Comment: 4 pages, 3 figures; final versio
Satisfying the Einstein-Podolsky-Rosen criterion with massive particles
In 1935, Einstein, Podolsky and Rosen (EPR) questioned the completeness of
quantum mechanics by devising a quantum state of two massive particles with
maximally correlated space and momentum coordinates. The EPR criterion
qualifies such continuous-variable entangled states, where a measurement of one
subsystem seemingly allows for a prediction of the second subsystem beyond the
Heisenberg uncertainty relation. Up to now, continuous-variable EPR
correlations have only been created with photons, while the demonstration of
such strongly correlated states with massive particles is still outstanding.
Here, we report on the creation of an EPR-correlated two-mode squeezed state in
an ultracold atomic ensemble. The state shows an EPR entanglement parameter of
0.18(3), which is 2.4 standard deviations below the threshold 1/4 of the EPR
criterion. We also present a full tomographic reconstruction of the underlying
many-particle quantum state. The state presents a resource for tests of quantum
nonlocality and a wide variety of applications in the field of
continuous-variable quantum information and metrology.Comment: 8 pages, 7 figure
Quantized form factor shift in the presence of free electron laser radiation
In electron scattering, the target form factors contribute significantly to
the diffraction pattern and carry information on the target electromagnetic
charge distribution. Here we show that the presence of electromagnetic
radiation, as intense as currently available in Free Electron Lasers, shifts
the dependence of the target form factors by a quantity that depends on the
number of photons absorbed or emitted by the electron as well as on the
parameters of the electromagnetic radiation. As example, we show the impact of
intense ultraviolet and soft X-ray radiation on elastic electron scattering by
Ne-like Argon ion and by Xenon atom. We find that the shift brought by the
radiation to the form factor is in the order of some percent. Our results may
open up a new avenue to explore matter with the assistance of laser
Mott-insulator phase of coupled 1D atomic gases in a 2D optical lattice
We discuss the 2D Mott insulator (MI) state of a 2D array of coupled finite
size 1D Bose gases. It is shown that the momentum distribution in the lattice
plane is very sensitive to the interaction regime in the 1D tubes. In
particular, we find that the disappearance of the interference pattern in time
of flight experiments will not be a signature of the MI phase, but a clear
consequence of the strongly interacting Tonks-Girardeau regime along the tubes.Comment: 4 pages, 3 figure
- …