225 research outputs found
Extracting the Mott gap from energy measurements in trapped atomic gases
We show that the measure of the so-called {\it release-energy}, which is an
experimentally accessible quantity, makes it possible to assess the value of
the Mott gap in the presence of the confinement potential that is unavoidable
in the actual experimental setup. Indeed, the curve of the release-energy as a
function of the total number of particles shows kinks that are directly related
to the existence of excitation gaps. Calculations are presented within the
Gutzwiller approach, but the final results go beyond this simple approximation
and represent a genuine feature of the real system. In the case of harmonic
confinement, the Mott gaps may be renormalized with respect to the uniform
case. On the other hand, in the case of the recently proposed off-diagonal
confinement, our results show an almost perfect agreement with the homogeneous
case.Comment: 4 pages and 5 figure
Characterization of the Bose-glass phase in low-dimensional lattices
We study by numerical simulation a disordered Bose-Hubbard model in
low-dimensional lattices. We show that a proper characterization of the phase
diagram on finite disordered clusters requires the knowledge of probability
distributions of physical quantities rather than their averages. This holds in
particular for determining the stability region of the Bose-glass phase, the
compressible but not superfluid phase that exists whenever disorder is present.
This result suggests that a similar statistical analysis should be performed
also to interpret experiments on cold gases trapped in disordered lattices,
limited as they are to finite sizes.Comment: 4+ epsilon pages and 4 figure
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