611 research outputs found
Dynamic Critical Phenomena in Trapped Bose Gases
Nonlinear dynamics of a trapped Bose-Einstein condensate, subject to the
action of a resonant external field, is studied. This field produces a
spatio-temporal modulation of the trapping potential with the frequency close
to the transition frequency between the ground state and a higher energy level.
The evolution equations of fractional populations display a kind of critical
phenomena at a critical line on the manifold of the system parameters. It is
demonstrated that there exists a direct analogy between dynamical instability
at this line and critical phenomena at a critical line of a related averaged
system.Comment: Latex file, 7 pages, no figure
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
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