共查询到20条相似文献,搜索用时 0 毫秒
1.
G. Tonini F. Werner Y. Castin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):283-294
We investigate theoretically the formation of a vortex lattice in
a superfluid two-spin component Fermi gas in a rotating harmonic trap, in a BCS-type
regime of condensed non-bosonic pairs.
Our analytical solution of the superfluid
hydrodynamic equations, both for the 2D BCS equation of state
and for the 3D unitary quantum gas, predicts that the vortex free gas is
subject to a dynamic instability for fast enough rotation.
With a numerical solution of the full
time dependent BCS equations in a 2D model, we confirm the existence of this dynamic
instability and we show that it leads to the formation of a regular pattern
of quantum vortices in the gas. 相似文献
2.
A. B. Bhattacherjee 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):499-506
We study the effect of a one dimensional optical superlattice on the superfluid properties (superfluid fraction, number squeezing,
dynamic structure factor) and the quasi-momentum distribution of the Mott-insulator. We show that due to the secondary lattice,
there is a decrease in the superfluid fraction and the number fluctuation. The dynamic structure factor which can be measured
by Bragg spectroscopy is also suppressed due to the addition of the secondary lattice. The visibility of the interference
pattern (the quasi-momentum distribution) of the Mott-insulator is found to decrease due to the presence of the secondary
lattice. Our results have important implications in atom interferometry and quantum computation in optical lattices. 相似文献
3.
K. P. Schmidt A. Reischl G. S. Uhrig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(2):343-352
In this work we give a consistent picture of the thermodynamic properties of
bosons in the Mott insulating phase when loaded adiabatically into
one-dimensional optical lattices. We find a crucial dependence of the
temperature in the optical lattice on the doping level of the Mott
insulator. In the undoped case, the temperature is of the order of the large
onsite
Hubbard interaction. In contrast, at a finite doping level the
temperature jumps almost immediately to the order of the small hopping
parameter. These two situations are investigated on the one hand by considering
limiting cases like the atomic limit and the case of free fermions. On the
other hand, they are examined using a quasi-particle conserving continuous
unitary transformation extended by an approximate thermodynamics for
hardcore particles. 相似文献
4.
H. M. Cataldo D. M. Jezek 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):585-590
We study the way in which the geometry of the trapping potential affects the vortex velocity in a Bose-Einstein condensate
confined by a toroidal trap. We calculate the vortex precession velocity through a simple relationship between such a velocity
and the gradient of the numerically obtained vortex energy. We observe that our results correspond very closely to the velocity
calculated through time evolution simulations. However, we find that the estimates derived from available velocity field formulas
present appreciable differences. To resolve such discrepancies, we further study the induced velocity field, analyzing the
effect of global features of the condensate on such a field and on the precession velocity. 相似文献
5.
J. Brand A. R. Kolovsky 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):331-336
The dynamics of a Bose-Einstein condensate is studied theoretically in a combined periodic plus harmonic external potential.
Different dynamical regimes of stable and unstable collective dipole and Bloch
oscillations are analysed in terms of a quantum mechanical pendulum
model. Nonlinear interactions are shown to counteract quantum-mechanical dephasing and lead to phase-coherent, superfluid
transport. 相似文献
6.
E. Lundh 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):517-520
Two effects are identified that affect the visibility of the
Mott transition in an atomic gas in an optical lattice confined
in a power-law potential. The transition can be made more
pronounced by increasing the power law, but at the same time,
experimental uncertainty in the number of particles will
induce corresponding fluctuations in the measured condensate
fraction. Calculations in two dimensions
indicate that a potential slightly more flat-bottomed than a
quadratic one is to be preferred for a wide range of
particle number fluctuation size. 相似文献
7.
Sk. Golam Ali B. Talukdar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):315-322
We consider matter-wave bright solitons in the presence of three-body atomic recombination, an axial periodic modulation and
a feeding term, and use a variational method to derive conditions to have dynamically stabilized solitons due to compensation
between the dissipation and alimentation of atoms from external sources. We critically examine how the BEC soliton is affected
by the imbalance between the internal atom loss and external feeding. We pay special attention
to study the influence of these terms on the soliton dynamics in optical lattice potentials that cause periodic modulation. 相似文献
8.
A. N. Salgueiro A.F.R. de Toledo Piza G. B. Lemos R. Drumond M. C. Nemes M. Weidemüller 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):537-540
The dynamics of the population imbalance of bosons in a double-well potential is investigated from the point of view of many-body
quantum mechanics in the framework of the two-mode
model.
For small initial population imbalances, coherent superpositions of almost equally spaced
energy eigenstates lead to Josephson oscillations. The suppression of tunneling at population imbalances beyond a critical
value is related to a high concentration of initial state population in the region of the energy spectrum with quasi-degenerate
doublets. Negligible coherences among adjacent doublets result in imbalance oscillations with a very small amplitude. For
unaccessible long times, however, the system recovers the regime of Josephson oscillations. 相似文献
9.
Y. Castin 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):317-328
We analytically solve two problems that may be useful in the context of the recent observation of matter wave bright solitons
in a one-dimensional attractive atomic Bose gas. The first problem is strictly beyond mean field: from the Bethe ansatz solution
we extract the internal correlation function of the particle positions in the quantum soliton, that is for a fixed center of mass position. The second problem is solved in the limit of a large number of particles, where the mean field theory
is asymptotically correct: it deals with the number of excitations created by the opening of the trap, starting from a pure
soliton in a weakly curved harmonic potential. 相似文献
10.
F. Li W. X. Shu J. G. Jiang H. L. Luo Z. Ren 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):355-361
Spatiotemporal dynamics of Bose-Einstein condensates in
moving optical lattices have been studied. For a weak lattice
potential, the perturbed correction to the heteroclinic orbit in a
repulsive system is constructed. We find the boundedness
conditions of the perturbed correction contain the Melnikov
chaotic criterion predicting the onset of Smale-horseshoe chaos.
The effect of the chemical potential on the spatiotemporal
dynamics is numerically investigated. It is revealed that the
variance of the chemical potential can lead the systems into
chaos. Regulating the intensity of the lattice potential can
efficiently suppress the chaos resulting from the variance of the
chemical potential. And then the effect of the phenomenological
dissipation is considered. Numerical calculation reveals that the
chaos in the dissipative system can be suppressed by adjusting the
chemical potential and the intensity of the lattice potential. 相似文献
11.
Z. Z. Chen Y. L. Ma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(1):163-170
The minimal energy configurations of finite Nv-body vortices in a
rotating trapped Bose-Einstein condensate is studied analytically by
extending the previous work [Y. Castin, R. Dum, Eur. Phys. J.
D 7, 399 (1999)], and taking into account the finite
size effects on z-direction and the bending of finite vortex lines. The
calculation of the energy of the vortices as a function of the rotation
frequency of the trap gives number, curvature, configuration of vortices and
width of vortex cores self-consistently. The numerical results show that (1)
the simplest regular polynomial of the several vortex configurations is
energetically favored; while the hexagonal vortex lattice is more stable
than square lattice; (2) bending is more stable then straight vortex line
along the z-axis for λ<1; (3) the boundary effect is obvious:
compared with the estimation made under infinite boundary, the finite size
effect leads to a lower vortex density, while the adding vortex bending
results in a less higher density because of the expansion. The results are
in well agreement with the other authors' ones. 相似文献
12.
M.-C. Chung A. R. Kolovsky 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):421-425
We consider a Bose-Einstein condensate of ultracold atoms loaded
into a square optical lattice and subject to a static force. For
vanishing atom-atom interactions the atoms perform periodic Bloch
oscillations for arbitrary direction of the force. We study
stability of these oscillations for non-vanishing interactions,
which is shown to depend on an alignment of the force vector with
respect to the lattice crystallographic axes. If the force is
aligned along any of the axes, the mean field approach can be used
to identify the stability conditions. On the contrary, for a
misaligned force one has to employ the microscopic approach, which
predicts periodic modulation of Bloch oscillations in the limit of a
large forcing. 相似文献
13.
R. Ramakumar A. N. Das 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(2):203-208
We present a theoretical study of bose condensation
of non-interacting bosons in finite lattices in quartic potentials in
one, two, and three dimensions. We investigate dimensionality
effects and quartic potential effects on single boson density of
energy states, condensation temperature, condensate fraction,
and specific heat. The results obtained are compared with
corresponding results for lattice bosons in harmonic traps. 相似文献
14.
L. Wang Y. Hao S. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(2):229-234
We investigate the quantum dynamics of repulsively bound atom
pairs in an optical lattice described by the periodic Bose-Hubbard
model both analytically and numerically. In the strongly repulsive
limit, we analytically study the dynamical problem by the
perturbation method with the hopping terms treated as a
perturbation. For a finite-size system, we numerically solve the
dynamic problem in the whole regime of interaction by the exact
diagonalization method. Our results show that the initially
prepared atom pairs are dynamically stable and the dissociation of
atom pairs is greatly suppressed when the strength of the on-site
interaction is much greater than the tunneling amplitude, i.e.,
the strongly repulsive interaction induces a self-localization
phenomenon of the atom pairs. 相似文献
15.
R. Ramakumar A. N. Das S. Sil 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):309-316
We present a theoretical study of Bose condensation and specific heat
of non-interacting bosons in finite lattices in harmonic potentials in
one, two, and three dimensions. We numerically diagonalize
the Hamiltonian to obtain the energy levels of the systems.
Using the energy levels thus obtained, we investigate the
temperature dependence, dimensionality effects, lattice size
dependence, and evolution to the bulk limit of the condensate
fraction and the specific heat. Some preliminary results on
the specific heat of fermions in optical lattices are also presented.
The results obtained are contextualized within the current experimental and
theoretical scenario. 相似文献
16.
T. P. Simula 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):453-455
We consider a quantized vortex excitation in a two-dimensional, harmonically trapped Bose gas and derive an equation for the
Berezinskii-Kosterlitz-Thouless transition temperature based on a simple free-energy argument. We relate the critical phase-space
density at the transition to the ratio between the entropy gain and the corresponding cost in energy of creating a free vortex
excitation in the system. 相似文献
17.
M. R. Zhang X. Y. Jiang Y. L. Zhang L. Shi J. Zi J. Y. Zhou 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(3):269-278
We systematically investigate slowly moving matter-wave gap
soliton propagation in weak random optical lattices. With the weak
randomness, an effective-particle theory is constructed to show
that the motion of a gap soliton is similar to a particle moving
in random potentials. Based on the effective-particle theory, the
effects of the randomness on gap solitons are obtained and the
trajectories of gap solitons are well predicted. Moreover, the
general laws that describe the movement depending on the weak
randomness are obtained. We find that with an increase of the
random strength, the ensemble-average velocity reduces slowly and
the reflection probability becomes larger. The theoretical results
based on the effective-particle theory are confirmed by the
numerical simulations based on the Gross-Pitaevskii equation. 相似文献
18.
B. Van Schaeybroeck A. Lazarides 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):329-333
We theoretically study the collective excitations of an ideal gas confined in an isotropic harmonic trap. We give an exact
solution to the Boltzmann-Vlasov equation; as expected for a single-component system, the associated mode frequencies are
integer multiples of the trapping frequency. We show that the expressions found by the scaling ansatz method are a special
case of our solution. Our findings are most useful in case the trap contains more than one phase: we demonstrate how to obtain
the oscillation frequencies in case an interface is present between the ideal gas and a different phase. 相似文献
19.
B. B. Baizakov B. A. Malomed M. Salerno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(2):367-374
The existence, stability and other dynamical properties of a new type of
multi-dimensional (2D or 3D) solitons supported by a transverse
low-dimensional (1D or 2D, respectively) periodic potential in the nonlinear
Schr?dinger equation with the self-defocusing cubic nonlinearity are
studied. The equation describes propagation of light in a medium with normal
group-velocity dispersion (GVD). Strictly speaking, solitons cannot exist in
the model, as its spectrum does not support a true bandgap. Nevertheless, the
variational approximation (VA) and numerical computations reveal stable
solutions that seem as completely localized ones, an explanation to which is
given. The solutions are of the gap-soliton type in the transverse
direction(s), in which the periodic potential acts in combination with the
diffraction and self-defocusing nonlinearity. Simultaneously, in the
longitudinal (temporal) direction these are ordinary solitons, supported by
the balance of the normal GVD and defocusing nonlinearity. Stability of the
solitons is predicted by the VA, and corroborated by direct simulations. 相似文献
20.
N. Bilas N. Pavloff 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):387-397
We study the elementary excitations of a transversely confined
Bose-Einstein condensate in presence of a weak axial random potential. We
determine the localization length (i) in the hydrodynamical low energy regime,
for a domain of linear densities ranging from the Tonks-Girardeau to the
transverse Thomas-Fermi regime, in the case of a white noise potential and
(ii) for all the range of energies, in the “one-dimensional mean field
regime”, in the case where the randomness is induced by a series of randomly
placed point-like impurities. We discuss our results in view of recent
experiments in elongated BEC systems. 相似文献