共查询到20条相似文献,搜索用时 15 毫秒
1.
E. Fersino B. A. Malomed G. Mussardo A. Trombettoni 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):417-426
We study the effect of an optical lattice (OL) on the ground-state properties of one-dimensional ultracold bosons with three-body
attractive interactions and two-body repulsive interactions, which are described by a cubic-quintic Gross-Pitaevskii equation
with a periodic potential. Without the optical lattice and with a vanishing two-body interaction term, normalizable soliton
solutions of the Townes type are possible only at a critical value of the interaction strength, at which an infinite degeneracy of the ground state
occurs; a repulsive two-body interaction makes such localized solutions unstable. We show that the OL opens a stability window
around the critical point when the strength of the periodic potential is above a critical threshold. We also consider the
effect of an external parabolic trap, studying how the stability properties depend on the matching between minima of the periodic
potential and the minimum of the parabolic trap. 相似文献
2.
Josephson oscillation of a superfluid Fermi gas 总被引:1,自引:0,他引:1
S. K. Adhikari 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):413-419
Using the complete numerical solution of a time-dependent
three-dimensional mean-field model we
study the Josephson oscillation of a superfluid Fermi gas (SFG) at zero temperature formed in a combined axially-symmetric
harmonic plus one-dimensional periodic optical-lattice (OL) potentials after displacing the harmonic trap along the axial
OL
axis. We study the dependence of Josephson frequency on the strength of the OL potential. The Josephson frequency decreases
with increasing strength as found in the experiment of Cataliotti et al. [Science 293, 843 (2001)] for a Bose-Einstein condensate and of the experiment of Pezzè et al. [Phys. Rev. Lett. 93, 120401 (2004)] for an ideal Fermi gas. We demonstrate a
breakdown of Josephson oscillation in the SFG for a large displacement
of the harmonic trap. These features of Josephson oscillation of a SFG can be tested experimentally. 相似文献
3.
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
4.
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
5.
I. E. Mazets J. Schmiedmayer 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):335-339
We provide a simple physical picture of the loss of coherence between two coherently split one-dimensional Bose-Einstein condensates.
The source of the dephasing is identified with nonlinear corrections to the elementary excitation energies in either of the
two independent condensates. We retrieve the result by Burkov, Lukin and Demler [Phys. Rev. Lett. 98, 200404 (2007)] on the subexponential decay of the coherence ∝exp [-(t/t0)2/3] for the large time t, however, the scaling of t0 differs. 相似文献
6.
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
7.
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
8.
We explore the many body physics of a Bose condensed atom gas at finite temperature through the Raman transition between two
hyperfine levels. Unlike the Bragg scattering where the phonon-like nature of the collective excitations has been observed,
a different branch of thermal atom excitation is found theoretically in the Raman scattering. This excitation is predicted
in the generalized random phase approximation (GRPA) and has a gapped and parabolic dispersion relation. The gap energy results
from the exchange interaction and is released during the Raman transition. The scattering rate is determined versus the transition
frequency ω and the transferred momentum q and shows the corresponding resonance around this gap. Nevertheless, the Raman
scattering process is attenuated by the superfluid part of the gas. The macroscopic wave function of the condensate deforms
its shape in order to screen locally the external potential displayed by the Raman light beams. This screening is total for
a condensed atom transition in order to prevent the condensate from incoherent scattering. The experimental observation of
this result would explain some of the reasons why asuperfluid condensate moves coherentlywithout any friction with its surrounding. 相似文献
9.
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
10.
R. Hoppeler J. Viana Gomes D. Boiron 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(1):157-162
We have studied the atomic density of a cloud confined
in an isotropic harmonic trap at the vicinity of the Bose-Einstein
transition temperature. We show that, for a non-interacting gas
and near this temperature, the ground-state density has the same
order of magnitude as the excited states density at the centre of
the trap. This holds in a range of temperatures where the
ground-state population is negligible compared to the total atom
number. We compare the exact calculations, available in a harmonic
trap, to semi-classical approximations. We show that these latter
should include the ground-state contribution to be accurate. 相似文献
11.
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
12.
Yun Li P. Treutlein J. Reichel A. Sinatra 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):365-381
We propose an analytical method to study the entangled spatial and spin dynamics of interacting bimodal Bose-Einstein condensates.
We show that at particular times during the evolution spatial and spin dynamics disentangle and the spin squeezing can be
predicted by a simple two-mode model. We calculate the maximum spin squeezing achievable in experimentally relevant situations
with Sodium or Rubidium bimodal condensates, including the effect of the dynamics and of one, two and three-body losses. 相似文献
13.
D. Nagy G. Szirmai P. Domokos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(1):127-137
The spatial self-organization of a Bose-Einstein condensate (BEC) in a high-finesse linear optical cavity is discussed. The
condensate atoms are laser-driven from the side and scatter photons into the cavity. Above a critical pump intensity the homogeneous
condensate evolves into a stable pattern bound by the cavity field. The transition point is determined analytically from a
mean-field theory. We calculate the lowest lying Bogoliubov excitations of the coupled BEC-cavity system and the quantum depletion
due to the atom-field coupling. 相似文献
14.
T. Enss W. Zwerger 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):383-389
We study the transition to fermion pair superfluidity in a mixture of interacting bosonic and fermionic atoms. The fermion
interaction induced by the bosons and the dynamical screening of the condensate phonons due to fermions are included using
the nonperturbative Hamiltonian flow equations. We determine the bosonic spectrum near the transition towards phase separation
and find that the superfluid transition temperature may be increased substantially due to phonon damping. 相似文献
15.
Sanjukta Roy Saptarishi Chaudhuri C. S. Unnikrishnan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(2):231-237
We discuss the expansion dynamics under mean-field repulsion of an array of 87Rb Bose-Einstein condensates produced in an all-optical scheme involving 1D lattice with nearly 105 atoms, after fast evaporative cooling of just about 1 s. Single site occupation exceeds 2 × 104 in our experiments. The possibility of transition to two-dimensionality was also investigated. The expansion behavior of
the high density multiple micro-condensates produced directly in the CO2 laser 1D optical lattice, with a lattice spacing of 5.3 μm, agrees well with a numerical simulation based on the mean-field
theory. 相似文献
16.
C. Miniatura R. C. Kuhn D. Delande C. A. Müller 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):353-364
This paper investigates quantum diffusion of matter waves in two-dimensional random potentials, focussing on expanding Bose-Einstein
condensates in spatially correlated optical speckle potentials. Special care is taken to describe the effect of dephasing,
finite system size, and an initial momentum distribution. We derive general expressions for the interference-renormalized
diffusion constant, the disorder-averaged probability density distribution, the variance of the expanding atomic cloud, and
the localized fraction of atoms. These quantities are studied in detail for the special case of an inverted-parabola momentum
distribution as obtained from an expanding condensate in the Thomas-Fermi regime. Lastly, we derive quantitative criteria
for the unambiguous observation of localization effects in a possible 2D experiment. 相似文献
17.
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
18.
A. Ruschhaupt A. del Campo J. G. Muga 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):399-403
A Bose-Einstein condensate may be prepared
in a harmonic trap with negligible
interatomic interactions using a Feshbach resonance.
If a strong repulsive interatomic interaction is switched on and
the trap is removed to let the condensate evolve freely,
a time dependent quantum interference pattern takes place in the short time
(Thomas-Fermi) regime, in which the number of peaks of the momentum
distribution increases one by one, whereas the spatial density barely changes.
The effect is stable for initial states with interactions and
realistic time-dependence of the scattering length. 相似文献
19.
H. Kuratsuji R. Botet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(1):111-116
We investigate a novel aspect of rotational tunneling of the macroscopic spin for multicomponent spinor Bose-Einstein condensate (BEC). The Lagrangian is deduced from
the multi-component BEC system formalism, and is written in terms of spin coherent states. From the effective Hamiltonian
for the collective spin, the tunneling rate is obtained through a functional integral of the spin variable. It is pointed
out that the cooperative effect between the Zeeman energy and the anisotropic nature of the spin-dependent inter-atomic interaction
plays a key role for occurrence of collective spin tunneling. 相似文献
20.
K. Howe A. R.P. Lima A. Pelster 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):667-682
Motivated by recent experiments on rotating Bose-Einstein condensates, we investigate a rotating, polarized Fermi gas trapped
in an anharmonic potential. We apply a semiclassical expansion of the density of states in order to determine how the thermodynamic
properties depend on the rotation frequency. The accuracy of the semiclassical approximation is tested and shown to be sufficient
for describing typical experiments. At zero temperature, rotating the gas above a given frequency ΩDO leads to a ‘donut’-shaped cloud which is analogous to the hole found in two-dimensional Bose-Einstein condensates. The free
expansion of the gas after suddenly turning off the trap is considered and characterized by the time and rotation frequency
dependence of the aspect ratio. Temperature effects are also taken into account and both low- and high-temperature expansions
are presented for the relevant thermodynamical quantities. In the high-temperature regime a virial theorem approach is used
to study the delicate interplay between rotation and anharmonicity. 相似文献