38 research outputs found
Fermi-Bose mixture in mixed dimensions
One of the challenging goals in the studies of many-body physics with
ultracold atoms is the creation of a topological superfluid
for identical fermions in two dimensions (2D). The expectations of reaching the
critical temperature through p-wave Feshbach resonance in spin-polarized
fermionic gases have soon faded away because on approaching the resonance, the
system becomes unstable due to inelastic-collision processes. Here, we consider
an alternative scenario in which a single-component degenerate gas of fermions
in 2D is paired via phonon-mediated interactions provided by a 3D BEC
background. Within the weak-coupling regime, we calculate the critical
temperature for the fermionic pair formation, using Bethe-Salpeter
formalism, and show that it is significantly boosted by higher-order
diagramatic terms, such as phonon dressing and vertex corrections. We describe
in detail an experimental scheme to implement our proposal, and show that the
long-sought p-wave superfluid is at reach with state-of-the-art experiments.Comment: 12 pages, 6 figures, 2 tables and supplementary materia
Tkachenko polarons in vortex lattices
We analyze the properties of impurities immersed in a vortex lattice formed
by ultracold bosons in the mean field quantum Hall regime. In addition to the
effects of a periodic lattice potential, the impurity is dressed by collective
modes with parabolic dispersion (Tkachenko modes). We derive the effective
polaron model, which contains a marginal impurity-phonon interaction. The
polaron spectral function exhibits a Lorentzian broadening for arbitrarily
small wave vectors even at zero temperature, in contrast with the result for
optical or acoustic phonons. The anomalous damping of Tkachenko polarons could
be detected experimentally using momentum-resolved spectroscopy.Comment: 10 pages, 2 figure
Free expansion of a Bose-Einstein condensate at the presence of a thermal cloud
We investigate numerically the free-fall expansion of a Rb atoms
condensate at nonzero temperatures. The classical field approximation is used
to separate the condensate and the thermal cloud during the expansion. We
calculate the radial and axial widths of the expanding condensate and find
clear evidence that the thermal component changes the dynamics of the
condensate. Our results are confronted against the experimental data
Collective excitation of a Bose-Einstein condensate by modulation of the atomic scattering length
We excite the lowest-lying quadrupole mode of a Bose-Einstein condensate by
modulating the atomic scattering length via a Feshbach resonance. Excitation
occurs at various modulation frequencies, and resonances located at the natural
quadrupole frequency of the condensate and at the first harmonic are observed.
We also investigate the amplitude of the excited mode as a function of
modulation depth. Numerical simulations based on a variational calculation
agree with our experimental results and provide insight into the observed
behavior.Comment: Submitted to PR