共查询到20条相似文献,搜索用时 0 毫秒
1.
W. Ketterle 《Physica B: Condensed Matter》2000,280(1-4):11-19
Bose–Einstein condensed atomic gases are a new class of quantum fluids. They are produced by cooling a dilute atomic gas to nanokelvin temperatures using laser and evaporative cooling techniques. The study of these quantum gases has become an interdisciplinary field of atomic and condensed matter physics. Topics of many-body physics can now be studied with the methods of atomic physics. Many long-standing predictions of the theory of the weakly interacting Bose gas have been verified, including thermodynamic properties of the phase transition and dynamic properties such as shape oscillations and sound propagation. Stimulated light scattering was used to determine the dynamic structure factor both in the phonon and free-particle regime. Atomic Bose condensates show a variety of novel phenomena which include multi-component spinor condensates, magnetic domain formation, miscibility and immiscibility of quantum fluids, and finite-size effects. 相似文献
2.
We discuss the energy eigenstates, ground and spin mixing dynamics of a spin-1 spinor Bose–Einstein condensate for a dilute atomic vapor confined in an optical trap. Our results go beyond the mean field picture and are developed within a fully quantized framework. 相似文献
3.
Using a novel magnetic trapping geometry we have evaporatively cooled metastable helium atoms to form a Bose–Einstein condensate containing approximately one million atoms. This is only the fourth demonstration of a metastable condensate and the first realisation of a BEC in a bi-planar quadrupole Ioffe configuration magnetic trap. 相似文献
4.
S. Jaakkola S. T. Boldarev A. A. Haritonov A. I. Safonov I. I. Lukashevich 《Physica B: Condensed Matter》2000,280(1-4):32-35
We report on new experiments at Turku where two-dimensional atomic hydrogen gas has been compressed magnetically to high degrees of quantum degeneracy on the surface of liquid 4He at about 200 mK. The results are in good agreement with our earlier observations: The probability of 3-body dipolar recombination is found to decrease gradually by an order of magnitude but to show no levelling yet, when the 2D phase-space density increases from 3 to 9. This effect is attributed mainly to a decrease in the local 3-particle correlator caused by the appearance and growth of a more or less local 2D condensate. The roles of interactions and out-of-plane delocalization of adsorbed H atoms are also discussed. 相似文献
5.
Masayoshi Nakano Ryohei Kishi Suguru Ohta Hideaki Takahashi Shin-ichi Furukawa Kizashi Yamaguchi 《Physica B: Condensed Matter》2005,370(1-4):110-120
We investigate the long-time dynamics of two-component dilute gas Bose–Einstein condensates with relatively different two-body interactions and Josephson couplings between the two components. Although in certain parameter regimes the quantum state of the system is known to evolve into macroscopic superposition, i.e., Schrödinger cat state, of two states with relative atom number differences between the two components, the Schrödinger cat state is also found to repeat the collapse and revival behavior in the long-time region. The dynamical behavior of the Pegg–Barnett phase difference between the two components is shown to be closely connected with the dynamics of the relative atom number difference for different parameters. The variation in the relative magnitude between the Josephson coupling and intra- and inter-component two-body interaction difference turns out to significantly change not only the size of the Schrödinger cat state but also its collapse–revival period, i.e., the lifetime of the Schrödinger cat state. 相似文献
6.
Using the idea of the macroscopic quantum wave function and the definition of the Melnikov chaos, we investigate the spatially chaotic features of a Bose–Einstein condensate (BEC) in a Wannier–Stark potential for the trivial phase and the non-trivial phase cases. The perturbed chaotic solutions are constructed, and the chaotic and unstable regions on the parameter space are illustrated. Numerical calculations to the spatial evolutions of the atomic number density and the energy density demonstrate the analytical results and exhibit the chaotic spatial distribution and energy distribution of the BEC atoms. 相似文献
7.
8.
Alexandru I. Nicolin Mogens H. Jensen Jan W. Thomsen R. Carretero-Gonzlez 《Physica D: Nonlinear Phenomena》2008,237(19):2476-2481
We consider the dynamics of a dilute, magnetically-trapped one-dimensional Bose–Einstein condensate whose scattering length is periodically modulated with a frequency that linearly increases in time. We show that the response frequency of the condensate locks to its eigenfrequency for appropriate ranges of the parameters. The locking sets in at resonance, i.e., when the effective frequency of driving field is equal to the eigenfrequency, and is accompanied by a sudden increase of the oscillations amplitude due to resonant energy transfer. We show that the dynamics of the condensate is given, to leading order, by a driven harmonic oscillator on the time-dependent part of the width of the condensate. This equation captures accurately both the locking and the resonant energy transfer as it is evidenced by comparison with direct numerical simulations of original Gross–Pitaevskii equation. 相似文献
9.
We reanalyze the non-linear population dynamics of a Bose–Einstein condensate (BEC) in a double well trap considering a semiclassical approach based on a time dependent variational principle applied to coherent states associated to SU(2) group. Employing a two-mode local approximation and hard sphere type interaction, we show in the Schwinger’s pseudo-spin language the occurrence of a fixed point bifurcation that originates a separatrix of motion on a sphere. This separatrix corresponds to the borderline between two dynamical regimes of Josephson oscillations and mesoscopic self-trapping. We also consider the effects of interaction between particles in different wells, known as cross-collisions. Such terms are usually neglected for traps sufficiently far apart, but recently it has been shown that they contribute to the effective tunneling constant with a factor growing linearly with the particle number. This effect changes considerably the effective tunneling of the system for sufficiently large number of trapped atoms, in perfect accord with experimental data. Finally, we identify analytically the transition parameter associated to the bifurcation in the generalized phase space of the model with cross-collision terms, and show how the dynamical regime depends on the initial conditions of the system and the collisional parameters values. 相似文献
10.
We calculate the quantum phase transition for a homogeneous Bose gas in the plane of s‐wave scattering length as and temperature T. This is done by improving a one‐loop result near the interaction‐free Bose‐Einstein critical temperature Tc(0) with the help of recent high‐loop results on the shift of the critical temperature due to a weak atomic repulsion based on variational perturbation theory. The quantum phase diagram shows a nose above Tc(0), so that we predict the existence of a reentrant transition above Tc(0), where an increasing repulsion leads to the formation of a condensate. 相似文献
11.
The Bose–Einstein condensation (BEC) in a binary mixture of Bose gases is studied by means of the Cornwall–Jackiw–Tomboulis (CJT) effective action approach. The equations of state (EoS) and various scenarios of phase transitions of the system are considered in detail, in particular, the numerical computations are carried out for symmetry restoration (SR), symmetry nonrestoration (SNR) and inverse symmetry breaking (ISB) for getting an insight into their physical nature. It is shown that due to the cross interaction between distinct components of mixture there occur two interesting phenomena: the high temperature BEC and the inverse BEC, which could be tested in experiments. 相似文献
12.
Sergey Tarasov William Shannon Vladimir Kocharovsky Vitaly Kocharovsky 《Entropy (Basel, Switzerland)》2022,24(12)
We propose a multi-qubit Bose–Einstein-condensate (BEC) trap as a platform for studies of quantum statistical phenomena in many-body interacting systems. In particular, it could facilitate testing atomic boson sampling of the excited-state occupations and its quantum advantage over classical computing in a full, controllable and clear way. Contrary to a linear interferometer enabling Gaussian boson sampling of non-interacting non-equilibrium photons, the BEC trap platform pertains to an interacting equilibrium many-body system of atoms. We discuss a basic model and the main features of such a multi-qubit BEC trap. 相似文献
13.
Zhi Lin 《Annalen der Physik》2021,533(1)
The phase boundaries of periodically driven spin–orbit coupled BECs with effective two‐body interactions are analytically calculated by using variational method. The phase diagrams of periodically driven and systems present distinguished features from undriven systems, respectively. For the BECs, the critical density (density at quantum tricritical point) will be dramatically reduced in some parameter regions, and the prospect of observing this intriguing quantum tricritical point is greatly enlarged. Moreover, a series of quantum tricritical points emerge quasi‐periodically when increasing the Raman coupling strength with fixed density. In the BECs, two hyperfine states of atoms can be miscible within the suitable regions of driving parameter space. As a result, systems will stay in the stripe phase with small Raman frequency at typical density, which expands the region of stripe phase in the phase diagram. In addition, an absence of quantum tricritical point in such system is observed, which is very unlike systems. 相似文献
14.
A continuation BSOR-Lanczos–Galerkin method for positive bound states of a multi-component Bose–Einstein condensate 总被引:1,自引:1,他引:1
Shu-Ming Chang Yuen-Cheng Kuo Wen-Wei Lin Shih-Feng Shieh 《Journal of computational physics》2005,210(2):439-458
We develop a continuation block successive over-relaxation (BSOR)-Lanczos–Galerkin method for the computation of positive bound states of time-independent, coupled Gross–Pitaevskii equations (CGPEs) which describe a multi-component Bose–Einstein condensate (BEC). A discretization of the CGPEs leads to a nonlinear algebraic eigenvalue problem (NAEP). The solution curve with respect to some parameter of the NAEP is then followed by the proposed method. For a single-component BEC, we prove that there exists a unique global minimizer (the ground state) which is represented by an ordinary differential equation with the initial value. For a multi-component BEC, we prove that m identical ground/bound states will bifurcate into m different ground/bound states at a finite repulsive inter-component scattering length. Numerical results show that various positive bound states of a two/three-component BEC are solved efficiently and reliably by the continuation BSOR-Lanczos–Galerkin method. 相似文献
15.
We show that Bose–Einstein condensation of charged scalar fields interacting with a topological gauge field at finite temperature is inhibited except for special values of the topological field. We also show that fermions interacting with this topological gauge field can condense for some values of the gauge field. 相似文献
16.
K N Shrivastava 《Pramana》1985,25(4):491-496
We find that in the spin-polarized hydrogen, Bose condensation occurs for certain quantized values of the magnetic field.
Once the field is fixed, sweeping of the radio-frequency results in nuclear magnetic resonance so that condensation and NMR
occur simultaneously. We have found that nuclear self-induced transparency occurs. A new excitation designated by the present
author as superboojum, which is a discontinuity in the hydrodynamic equations in spin-polarized hydrogen having finite nuclear
as well as electronic spin is discovered. 相似文献
17.
A system of charged bosons at finite temperature and chemical potential is studied in a general-relativistic framework. We assume that the boson fields interact only gravitationally. At sufficiently low temperature the system exists in two phases: the gas and the condensate. By studying the condensation process numerically we determine the critical temperature Tc at which the condensate emerges. As the temperature decreases, the system eventually settles down in the ground state of a cold boson star. 相似文献
18.
We consider the interaction between an f-deformed Bose–Einstein condensate and a single-mode quantized light field. By using the Gardiner’s phonon operators, we find that there exists a natural deformation in the model which modifies the Bogoliubov approximation under the condition of large but finite number of particles in condensate. This approach introduces an intrinsically deformed Bose–Einstein condensate, where the deformation parameter, well-defined by the particle number N in condensate, controls the strength of the associated nonlinearity. By introducing the deformed Gardiner’s phonon operators we modify the very dilute-gas approximation through including atomic collisions in condensate. The rate of atomic collisions κ, as a new deformation parameter in the deformed Bose–Einstein condensate, controls the nonlinearity related to the atomic collisions. We show that by controlling the nonlinearities in the f-deformed atomic condensate through the two atomic parameters N and κ, it is possible to generate and manipulate the nonclassical quantum statistical properties of radiation field, such as, the sub-Poissonian photon statistics and quadrature squeezing. Also, it is possible to control the collapses and revivals phenomena in the average number of photons by atomic parameters N and κ. 相似文献
19.
L. J. Garay 《International Journal of Theoretical Physics》2002,41(11):2073-2090
It is shown that there exist both dynamically stable and unstable dilute-gas Bose–Einstein condensates that, in the hydrodynamic limit, exhibit a behavior completely analogous to that of gravitational black holes. The dynamical instabilities involve creation of quasiparticle pairs in positive and negative energy states. We illustrate these features in two qualitatively different one-dimensional models. We have also simulated the creation of a stable sonic black hole by solving the Gross–Pitaevskii equation numerically for a condensate subject to a trapping potential that is adiabatically deformed. A sonic black hole could in this way be created experimentally with state-of-the-art or planned technology. 相似文献
20.
Alain Junod Marlyse Roulin Bernard Revaz Andreas Erb 《Physica B: Condensed Matter》2000,280(1-4):214-219
Thermal fluctuations are observed in the specific heat of high-temperature superconductors (HTS) near Tc. This is seen both in the shape of the zero-field anomaly, characterized by critical exponents and amplitude ratios, and in the broadening of the transition versus the magnetic field, which obeys scaling laws. 3D-XY fluctuations are found for YBa2Cu3Ox (Y-123) near optimal doping, whereas systematic deviations occur away from this point. The large deviations found for the most anisotropic HTS may be attributed to both reduced dimensionality and a crossover between BCS and Bose condensations. Low-temperature data are discussed in this context. The melting curve of vortex matter, now detected in the specific heat of Dy-123, Eu-123 and Y-123 up to very high fields, is described by a critical exponent. 相似文献