共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
X. Deng R. Citro E. Orignac A. Minguzzi 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):435-443
Using exact diagonalisation and Density Matrix Renormalisation group (DMRG) approach we analyse the transition to a localised
state of a weakly interacting quasi-1D Bose gas subjected to a quasiperiodic potential. The analysis is performed by calculating
the superfluid fraction, density profile, momentum distribution and visibility for different periodicities of the second lattice
and in the presence (or not) of a weak repulsive interaction. It is shown that the transition is sharper towards the maximally
incommensurate ratio between the two lattice periodicities, and shifted to higher values of the second lattice strength by
weak repulsive interactions. We also relate our results to recent experiments. 相似文献
3.
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
4.
Y. Hao Y. Zhang J. Q. Liang S. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):541-545
We investigate the effect of the anisotropic spin-spin interaction
on the ground state density distribution of the one dimensional
spin-1 bosonic gases within a modified Gross-Pitaevskii theory
both in the weakly interaction regime and in the Tonks-Girardeau
(TG) regime. We find that for ferromagnetic spinor gas the phase
separation occurs even for weak anisotropy of the spin-spin
interaction, which becomes more and more obvious and the component
of mF=0 diminishes as the anisotropy increases. However, no
phase separation is found for anti-ferromagnetic spinor gas in
both regimes. 相似文献
5.
We investigate the interactions between components of various vector solitons in Bos-Einstein condensates by means of the least action principle, and derive the effective potentials for different vector solitons, which indicate that the interactions are of short range, and may be repulsive or attractive decided by the different intra- and inter-species interactions in such a system. In the case of attraction, the two solitons will oscillate about and pass through each other around the equilibrium state. The comparison of analytical results with mumertical simulation is presented. 相似文献
6.
M. Takahashi S. Ghosh T. Mizushima K. Machida 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):391-400
We show that the effective theory of long wavelength low energy behavior of a dipolar Bose-Einstein condensate(BEC) with large
dipole moments (treated as a classical spin) can be modeled using an extended non-linear sigma model (NLSM) like energy functional
with an additional non-local term that represents long ranged anisotropic dipole-dipole interaction. Minimizing this effective
energy functional we calculate the density and spin-profile of the dipolar Bose-Einstein condensate in the mean-field regime
for various trapping geometries. The resulting configurations show strong intertwining between the spin and mass density of
the condensate, transfer between spin and orbital angular momentum in the form of Einstein-de Hass effect, and novel topological
properties. We have also described the theoretical framework in which the collective excitations around these mean field solutions
can be studied and discuss some examples qualitatively. 相似文献
7.
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
8.
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
9.
10.
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
11.
C. Trallero-Giner V. López-Richard Joseph L. Birman 《Physica D: Nonlinear Phenomena》2008,237(18):2342-2352
Considering the Gross-Pitaevskii integral equation we are able to formally obtain an analytical solution for the order parameter Φ(x) and for the chemical potential μ as a function of a unique dimensionless non-linear parameter Λ. We report solutions for different ranges of values for the repulsive and the attractive non-linear interactions in the condensate. Also, we study a bright soliton-like variational solution for the order parameter for positive and negative values of Λ. Introducing an accumulated error function we have performed a quantitative analysis with respect to other well-established methods as: the perturbation theory, the Thomas-Fermi approximation, and the numerical solution. This study gives a very useful result establishing the universal range of the Λ-values where each solution can be easily implemented. In particular, we showed that for Λ<−9, the bright soliton function reproduces the exact solution of GPE wave function. 相似文献
12.
We calculate the reflection probability for ultracold alkali atoms incident on a solid surface. By considering the interatomic interaction and using the WKB method, it is shown that the repulsive interaction between atoms has the effect of increasing the reflection probability. The increasing amplitude is related with the interatomic interaction and the depth of atom-surface potential. In addition, we also perform a numerical calculation to testify the effect of the interatomic interaction, and the analytic result is proven by the numerical result. 相似文献
13.
Coupling between Collective Excitations of a Bose--Einstein Condensate and Modulated Interactions 下载免费PDF全文
We investigate collective excitations of a Bose Einstein repulsive interactions, and analytically demonstrate that condensate in the presence of temporal modulation of the modulated interaction can drive the condensate to oscillate with the external modulation frequency, and that the interaction couples with the eigen modes of the condensate collective excitations, which was previously considered to be independent of interaction. When the external modulation frequency approaches or is far away from the eigen frequency of the density monopole mode, the condensate shows resonant or beating behaviour. 相似文献
14.
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
15.
C. J. Tessone D. H. Zanette R. Toral 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):319-326
We study the influence of repulsive interactions on an
ensemble of coupled excitable rotators. We find that a moderate
fraction of repulsive interactions can trigger global firing of the
ensemble. The regime of global firing, however, is suppressed in
sufficiently large systems if the network of repulsive interactions
is fully random, due to self-averaging in its degree distribution.
We thus introduce a model of partially random networks with a broad
degree distribution, where self-averaging due to size growth is
absent. In this case, the regime of global firing persists for large
sizes. Our results extend previous work on the constructive effects
of diversity in the collective dynamics of complex systems. 相似文献
16.
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
17.
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
18.
Ground-State Properties of Charged Bosons Confined in a One-Dimensional Harmonic Double-Well Trap: Diffusion Monte Carlo Calculations 下载免费PDF全文
The diffusion Monte Carlo method is applied to study the ground-state properties of charged bosons in one dimension confined in a harmonic double-well trap. The particles interact repulsively through a Coulombic 1/r potential. Numerical results show that the well separation has significant influence on the ground-state properties of the system. When the interaction of the system is weak, ground-state energy decreases with the increasing well separation and has a minimal value. If the well separation increases continually~ the ground-state energy increases and approaches to a constant gradually. This effect will be abatable in the strong interacting system. In addition, by calculating the density of the systems for different interaction strengths with various well separations, we find that the density increases abnormally when the well separation is large at the centre of the system. 相似文献
19.
20.
M. Nakano S. Ohta R. Kishi H. Takahashi S. Furukawa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(3):523-532
We investigate the relaxation effects on the dynamics of two-component
dilute gas Bose-Einstein condensates (BEC) with relatively different
two-body interactions and Josephson couplings between the two components.
Three types of relaxation effects, i.e., one- and three-body losses and a
pure phase relaxation caused by elastic two-body collision between condensed
and noncondensed atoms, are examined on the dynamical behavior of a
macroscopic superposition, i.e., Schr?dinger cat state, of two states
with atom-number differences between the two components, which is known to
be created by the time evolution in certain parameter regimes. Although
three-body losses show a relatively large suppression of the revival
behavior of Schr?dinger cat state and the Pegg-Barnett phase-difference
distribution between the two components for a small-size Schr?dinger cat
state, one- and three-body loss effects are not shown to directly depend on
the size of Schr?dinger cat state. In contrast, the pure-phase
relaxation effects, causing a reduction of phase-difference distribution and
then decaying the Schr?dinger cat state, significantly increase with the
increase of the size of Schr?dinger cat state. These features suggest
that a detection of damped collapse-revival behavior is highly possible for
medium-size Schr?dinger cat states in small-size two-component BECs. 相似文献