



01747nas a2200157   4500008004100000245008800041210006900129260001500198300001100213490000700224520127000231100001801501700001501519700001901534856003601553       2016                        eng d00aSudden-quench dynamics of Bardeen-Cooper-Schrieffer states in deep optical lattices0 aSuddenquench dynamics of BardeenCooperSchrieffer states in deep   c2016/08/05  a0236070 v943 a<p>We determine the exact time evolution of an initial Bardeen-Cooper-Schrieffer (BCS) state of ultra-cold atoms in a hexagonal optical lattice. The dynamical evolution is triggered by ramping the lattice potential up, such that the interaction strength Uf is much larger than the hopping amplitude Jf. The quench initiates collective oscillations with frequency |Uf|/(2π) in the momentum occupation numbers and imprints an oscillating phase with the same frequency on the order parameter Δ. The latter is not reproduced by treating the time evolution in mean-field theory. The momentum density-density or noise correlation functions oscillate at frequency |Uf|/2π as well as its second harmonic. For a very deep lattice, with negligible tunneling energy, the oscillations of momentum occupation numbers are undamped. Non-zero tunneling after the quench leads to dephasing of the different momentum modes and a subsequent damping of the oscillations. This occurs even for a finite-temperature initial BCS state, but not for a non-interacting Fermi gas. We therefore propose to use this dephasing to detect a BCS state. Finally, we predict that the noise correlation functions in a honeycomb lattice will develop strong anti-correlations near the Dirac point.</p>1 aNuske, Marlon1 aMathey, L.1 aTiesinga, Eite  uhttp://arxiv.org/abs/1602.0097901328nas a2200157   4500008004100000245008400041210006900125260001500194300001100209490000700220520085400227100001801081700001901099700001501118856003701133       2015                        eng d00aOptimization of collisional Feshbach cooling of an ultracold  nondegenerate gas0 aOptimization of collisional Feshbach cooling of an ultracold non  c2015/04/20  a0436260 v913 a  We optimize a collision-induced cooling process for ultracold atoms in the
nondegenerate regime. It makes use of a Feshbach resonance, instead of rf
radiation in evaporative cooling, to selectively expel hot atoms from a trap.
Using functional minimization we analytically show that for the optimal cooling
process the resonance energy must be tuned such that it linearly follows the
temperature. Here, optimal cooling is defined as maximizing the phase-space
density after a fixed cooling duration. The analytical results are confirmed by
numerical Monte-Carlo simulations. In order to simulate more realistic
experimental conditions, we show that background losses do not change our
conclusions, while additional non-resonant two-body losses make a lower initial
resonance energy with non-linear dependence on temperature preferable.
1 aNuske, Marlon1 aTiesinga, Eite1 aMathey, L.  uhttp://arxiv.org/abs/1412.8473v101241nas a2200181   4500008004100000245007500041210006900116260001500185490000700200520070200207100001300909700001500922700001900937700002000956700002300976700002300999856003701022       2011                        eng d00aDetecting paired and counterflow superfluidity via dipole oscillations0 aDetecting paired and counterflow superfluidity via dipole oscill  c2011/10/270 v843 a  We suggest an experimentally feasible procedure to observe paired and
counterflow superfluidity in ultra-cold atom systems. We study the time
evolution of one-dimensional mixtures of bosonic atoms in an optical lattice
following an abrupt displacement of an additional weak confining potential. We
find that the dynamic responses of the paired superfluid phase for attractive
inter-species interactions and the counterflow superfluid phase for repulsive
interactions are qualitatively distinct and reflect the quasi long-range order
that characterizes these states. These findings suggest a clear experimental
procedure to detect these phases, and give an intuitive insight into their
dynamics.
1 aHu, Anzi1 aMathey, L.1 aTiesinga, Eite1 aDanshita, Ippei1 aWilliams, Carl, J.1 aClark, Charles, W.  uhttp://arxiv.org/abs/1103.3513v301378nas a2200157   4500008004100000245007600041210006900117260001300186490000700199520090300206100001301109700001501122700002301137700002301160856003701183       2010                        eng d00aNoise correlations of one-dimensional Bose mixtures in optical lattices0 aNoise correlations of onedimensional Bose mixtures in optical la  c2010/6/20 v813 a  We study the noise correlations of one-dimensional binary Bose mixtures, as a
probe of their quantum phases. In previous work, we found a rich structure of
many-body phases in such mixtures, such as paired and counterflow
superfluidity. Here we investigate the signature of these phases in the noise
correlations of the atomic cloud after time-of-flight expansion, using both
Luttinger liquid theory and the time-evolving block decimation (TEBD) method.
We find that paired and counterflow superfluidity exhibit distinctive features
in the noise spectra. We treat both extended and inhomogeneous systems, and our
numerical work shows that the essential physics of the extended systems is
present in the trapped-atom systems of current experimental interest. For
paired and counterflow superfluid phases, we suggest methods for extracting
Luttinger parameters from noise correlation spectroscopy.
1 aHu, Anzi1 aMathey, L.1 aWilliams, Carl, J.1 aClark, Charles, W.  uhttp://arxiv.org/abs/1002.4918v201137nas a2200157   4500008004100000245008200041210006900123260001300192490000700205520065000212100001500862700001900877700002300896700002300919856003700942       2009                        eng d00aCollisional cooling of ultra-cold atom ensembles using Feshbach  resonances
0 aCollisional cooling of ultracold atom ensembles using Feshbach r  c2009/9/80 v803 a  We propose a new type of cooling mechanism for ultra-cold fermionic atom
ensembles, which capitalizes on the energy dependence of inelastic collisions
in the presence of a Feshbach resonance. We first discuss the case of a single
magnetic resonance, and find that the final temperature and the cooling rate is
limited by the width of the resonance. A concrete example, based on a p-wave
resonance of $^{40}$K, is given. We then improve upon this setup by using both
a very sharp optical or radio-frequency induced resonance and a very broad
magnetic resonance and show that one can improve upon temperatures reached with
current technologies.
1 aMathey, L.1 aTiesinga, Eite1 aJulienne, Paul, S.1 aClark, Charles, W.  uhttp://arxiv.org/abs/0903.2568v101819nas a2200181   4500008004100000245009700041210006900138260001400207490000700221520125900228100001301487700001501500700002001515700001901535700002301554700002301577856003701600       2009                        eng d00aCounterflow and paired superfluidity in one-dimensional Bose mixtures in  optical lattices
0 aCounterflow and paired superfluidity in onedimensional Bose mixt  c2009/8/240 v803 a  We study the quantum phases of mixtures of ultra-cold bosonic atoms held in
an optical lattice that confines motion or hopping to one spatial dimension.
The phases are found by using Tomonaga-Luttinger liquid theory as well as the
numerical method of time evolving block decimation (TEBD). We consider a binary
mixture with repulsive intra-species interactions, and either repulsive or
attractive inter-species interaction. For a homogeneous system, we find paired-
and counterflow-superfluid phases at different filling and hopping energies. We
also predict parameter regions in which these types of superfluid order coexist
with charge density wave order. We show that the Tomonaga-Luttinger liquid
theory and TEBD qualitatively agree on the location of the phase boundary to
superfluidity. We then describe how these phases are modified and can be
detected when an additional harmonic trap is present. In particular, we show
how experimentally measurable quantities, such as time-of-flight images and the
structure factor, can be used to distinguish the quantum phases. Finally, we
suggest applying a Feshbach ramp to detect the paired superfluid state, and a
$\pi/2$ pulse followed by Bragg spectroscopy to detect the counterflow
superfluid phase.
1 aHu, Anzi1 aMathey, L.1 aDanshita, Ippei1 aTiesinga, Eite1 aWilliams, Carl, J.1 aClark, Charles, W.  uhttp://arxiv.org/abs/0906.2150v1