3 research outputs found
Noise Correlations in one-dimensional systems of ultra-cold fermions
Time of flight images reflect the momentum distribution of the atoms in the
trap, but the spatial noise in the image holds information on more subtle
correlations. Using Bosonization, we study such noise correlations in generic
one dimensional systems of ultra cold fermions. Specifically, we show how
pairing as well as spin and charge density wave correlations may be identified
and extracted from the time of flight images. These incipient orders manifest
themselves as power law singularities in the noise correlations, that depend on
the Luttinger parameters, which suggests a general experimental technique to
obtain them.Comment: 5 pages, 3 figures. Added discussion on the visibility of noise
correlation features for realistic condition
Noise Correlations in low-dimensional systems of ultracold atoms
We derive relations between standard order parameter correlations and the
noise correlations in time of flight images, which are valid for systems with
long range order as well as low dimensional systems with algebraic decay of
correlations. Both Bosonic and Fermionic systems are considered. For one
dimensional Fermi systems we show that the noise correlations are equally
sensitive to spin, charge and pairing correlations and may be used to
distinguish between fluctuations in the different channels. This is in contrast
to linear response experiments, such as Bragg spectroscopy, which are only
sensitive to fluctuations in the particle-hole channel (spin or charge). For
Bosonic systems we find a sharp peak in the noise correlation at opposite
momenta that signals pairing correlations in the depletion cloud. In a
condensate with true long range order, this peak is a delta function and we can
use Bogoliubov theory to study its temperature dependence. Interestingly we
find that it is enhanced with temperature in the low temperature limit. In one
dimensional condensates with only quasi-long range (i.e. power-law) order the
peak in the noise correlations also broadens to a power-law singularity.Comment: 14 pages, 7 figure
Noise Correlations of Hard-core Bosons: Quantum Coherence and Symmetry Breaking
Noise correlations, such as those observable in the time of flight images of
a released cloud, are calculated for hard-core bosonic (HCB) atoms. We find
that the standard mapping of HCB systems onto spin-1/2 XY models fails in
application to computation of noise correlations due to the contribution of
multiply occupied virtual states in HCB systems. Such states do not exist in
spin models. An interesting manifestation of such states is the breaking of
particle-hole symmetry in HCB. We use noise correlations to explore quantum
coherence of strongly correlated bosons in the fermionized regime with and
without external parabolic confinement. Our analysis points to distinctive new
experimental signatures of the Mott phase.Comment: 17 pages, 6 figures. This is a detailed revised version of
quant-ph/0507153. It has been submitted to Journal of Physics B: the special
edition for the Cortona BEC worksho