共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
Y. J. Hao S. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(2):261-266
We study ground-state properties of interacting two-component boson gases in a one-dimensional harmonic trap by using the
exact numerical diagonalization method. Based on numerical solutions of many-body Hamiltonians, we calculate the ground-state
density distributions in the whole interaction regime for different atomic number ratio, intra- and inter-atomic interactions.
For the case with equal intra- and inter-atomic interactions, our results clearly display the evolution of density distributions
from a Bose condensate distribution to a Fermi-like distribution with the increase of the repulsive interaction. Particularly,
we compare our result in the strong interaction regime to the exact result in the infinitely repulsive limit which can be
obtained by a generalized Bose-Fermi mapping. We also discuss the general case with different intra- and inter-atomic interactions
and show the rich configurations of the density profiles. 相似文献
3.
H. Kuratsuji R. Botet 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(3):445-454
The dynamics of the collective spin for Bose-Einstein condensates with nonlinear interactions, is studied within the framework
of the two-component spinor. We discuss the
spin resonance when the system is submitted to a periodically-modulated magnetic field at the zero temperature. In this case,
the nonlinearity parameter controls the critical change between a localized and a homogeneous spin state. When the temperature
is finite – or a random magnetic field is considered – the movement of the collective spin is governed by the Landau-Lifshitz-Gilbert
equation, from which the complete Fokker-Planck equation is derived. This equation is the essential tool to describe the time-evolution
of the probability distribution function for the collective spin. The functional integral approach is used to solve analytically
examples of BEC spin behavior in a static magnetic field at finite temperature. We show how such a method can lead effectively
to the complete solution of the Fokker-Planck equation for this kind of problems. 相似文献
4.
Y.-M. Kao T. F. Jiang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(2):263-269
The thermodynamic properties of the trapped ideal spinor Bose gas are
studied in details with the constraints of fixed total number of atoms N, and
magnetization M. The double transition temperatures, their
corresponding corrections due to finite particle number, and the
population of each component are investigated. The generalization
to the ideal spinor Bose gas of hyperfine quantum number F is
also discussed. We propose that the order and disorder parameters
to describe the symmetry broken of condensation. 相似文献
5.
N. Bera J. K. Bhattacharjee 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(1):21-26
An exact calculation of the Casimir force for a non-interacting Bose gas confined between two parallel plates is presented. The gas can be free or trapped, parallel to the plates. Depending on the finite size parameter λ/L (λ is the de Bröglie wavelength and L is the separation of the plates) and the density parameter nλ3 (n, the number density), the Casimir force crosses over from a power law to an exponential fall off is clearly seen. Since the Casimir force measurement requires very small values of L, one needs to take into account of the condensation in a finite system. 相似文献
6.
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
7.
Shyamal Biswas 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):109-112
We study the Bose-Einstein condensation for a 3-d system of ideal Bose gas which is harmonically trapped along two perpendicular
directions and is confined in between two slabs along the other perpendicular direction. We calculate the Casimir force between
the two slabs for this system of trapped Bose gas. At finite temperatures this force for thermalized photons in between two
plates has a classical expression which is independent of ħ. At finite temperatures the Casimir force for our system depends
on ħ. For the calculation of Casimir force we consider only the Dirichlet boundary condition. We show that below condensation
temperature (Tc) the Casimir force for this non-interacting system decreases with temperature (T) and at
, it is independent of temperature. We also discuss the Casimir effect on 3-d highly anisotropic harmonically trapped ideal
Bose gas. 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.
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
10.
S. Röthel A. Pelster 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(3):343-356
We analyze in detail recent experiments on ultracold dilute 87Rb–40K mixtures in Hamburg and in Florence within a mean-field theory. To this end we determine how the stationary bosonic and
fermionic density profiles in this mixture depend in the Thomas-Fermi limit on the respective particle numbers. Furthermore,
we investigate how the observed stability of the Bose-Fermi mixture with respect to collapse is crucially related to the value
of the interspecies s-wave scattering length. 相似文献
11.
E. P. Zemskov K. Kassner M. A. Tsyganov M. J.B. Hauser 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(3):457-465
Using a field-theoretic approach, we systematically generalize the usual semiclassical approximation for a harmonically trapped
ideal Bose gas in such a way that its range of applicability is essentially extended. With this we can analytically calculate
thermodynamic properties even for small particle numbers. In particular, it now becomes possible to determine the critical
temperature as well as the temperature dependence of both heat capacity and condensate fraction in low-dimensional traps,
where the standard semiclassical approximation is not even applicable. 相似文献
12.
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
13.
D. Guerra R. Méndez-Galain N. Wschebor 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(3):357-365
The usual procedure of including a finite number of vertices in Non Perturbative Renormalization Group equations in order
to obtain n-point correlation functions at finite momenta is analyzed.
This is done by exploiting a general method recently introduced which includes simultaneously all vertices
although approximating their momentum dependence. The study is performed using the self-energy of the tridimensional scalar
model at criticality.
At least in this example, low order truncations miss quantities as the critical exponent η by as much as 60%. However, if
one goes to high order truncations the procedure seems to converge rapidly. 相似文献
14.
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
15.
S. K. Adhikari 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):279-286
Using variational and numerical solutions we show that
stationary
negative-energy localized (normalizable) bound states can appear in the
three-dimensional nonlinear Schr?dinger equation with a finite
square-well potential for a range of nonlinearity parameters. Below a
critical attractive nonlinearity, the system becomes unstable and
experiences collapse. Above a limiting repulsive nonlinearity, the
system becomes highly repulsive and cannot be bound. The system also
allows nonnormalizable states of infinite norm at positive energies in
the continuum. The normalizable negative-energy bound states could be
created in BECs and studied in the laboratory with present knowhow. 相似文献
16.
A. E. Bernardini 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):151-155
The quartic confining potential has emerged as a key ingredient to obtain
fast rotating vortices in BEC as well as observation of quantum phase
transitions in optical lattices. We calculate the critical temperature
Tc of bosons at which normal to BEC transition occurs for the quartic
confining potential. Further more, we evaluate the effect of finite
particle number on Tc and find that ΔTc/Tc is
larger in quartic potential as compared to quadratic potential for number
of particles <105. Interestingly, the situation is reversed if
the number of particles is
105. 相似文献
17.
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
18.
P. Buonsante S. M. Giampaolo F. Illuminati V. Penna A. Vezzani 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):427-433
We consider strongly interacting boson-boson mixtures on one-dimensional lattices and, by adopting a qualitative mean-field
approach, investigate their quantum phases as the interspecies repulsion is increased. In particular, we analyze the low-energy
quantum emulsion metastable states occurring at large values of the interspecies interaction, which are expected to prevent the system from
reaching its true ground state. We argue a significant decrease in the visibility of the time-of-flight images in the case
of these spontaneously disordered states. 相似文献
19.
Stefano De Leo Pietro Rotelli 《The European Physical Journal C - Particles and Fields》2009,62(4):793-797
We develop the potential scattering of a spinor within the context of perturbation field theory. As an application, we reproduce,
up to second order in the potential, the diffusion results for a potential barrier of quantum mechanics. An immediate consequence
is a simple generalization to arbitrary potential forms, a feature not possible in quantum mechanics. 相似文献
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