Classical fields approximation for bosons at nonzero temperatures

Brewczyk, Mirosław; Gajda, Mariusz; Rza̧żewski, Kazimierz

doi:10.1088/0953-4075/40/2/r01

Cited by 99 publications

(167 citation statements)

References 87 publications

Supporting

Mentioning

167

Contrasting

Order By: Relevance

“…An alternative approach to simulate the dynamics of BECs at finite temperature is the classical field, or c-field methodology [49][50][51]. Intuitively, a classical field treatment of a BEC will be a reasonable approximation when the system has a significant number of modes with large occupation numbers n i = k B T / i 1, where i is the energy of the mode [52].…”

Section: Appendix A: Classical Field Simulationsmentioning

confidence: 99%

Collapse and revival of the monopole mode of a degenerate Bose gas in an isotropic harmonic trap

et al. 2016

View full text Add to dashboard Cite

We study the monopole (breathing) mode of a finite temperature Bose-Einstein condensate in an isotropic harmonic trap recently developed by Lobser et al. [Nat. Phys. 11, 1009(2015]. We observe a nonexponential collapse of the amplitude of the condensate oscillation followed by a partial revival. This behavior is identified as being due to beating between two eigenmodes of the system, corresponding to in-phase and out-of-phase oscillations of the condensed and noncondensed fractions of the gas. We perform finite temperature simulations of the system dynamics using the Zaremba-Nikuni-Griffin methodology [J. Low Temp. Phys. 116, 277 (1999)], and find good agreement with the data, thus confirming the two mode description.

show abstract

Section: Appendix A: Classical Field Simulationsmentioning

confidence: 99%

Collapse and revival of the monopole mode of a degenerate Bose gas in an isotropic harmonic trap

et al. 2016

View full text Add to dashboard Cite

show abstract

“…1, we can see that the splitting produces excitations which may diminish the condensate fraction. To analyze the condensate fraction, one needs the so-called c-field approach [40][41][42]. Such an analysis is helpful to evaluate the performance of atomic beam splitters.…”

Section: Discussionmentioning

confidence: 99%

Splitting dynamics of a two-species Bose-Einstein condensate in two translating traps

Sun

Pindzola

2011

Open Physics

View full text Add to dashboard Cite

Abstract:We extend our previous work of splitting a single-species Bose-Einstein condensate in two translating traps to a two-species condensate. Different from the single species case where interaction is considered as a damping mechanism to the motion of the condensate, we find that, in the two species case, the damping effect is much less obvious and the splitting dynamics exhibit different behaviors. The distribution of each component are not damped towards 50:50 for large interaction strength in the two wells. Our conclusions are supported by investigating the dependence of the splitting on both the translation speed and the interspecies scattering length. PACS

show abstract

“…Recently, we have shown that dark solitons are spontaneously generated in quasi-one-dimensional Bose gases at equilibrium [16]. By analyzing the statistical distributions of excitations within both the Lieb-Liniger model [17] and the classical fields approximation [18,19] we proved that type II excitations are indeed quantum solitons [20].…”

mentioning

confidence: 90%

“…Each classical field belonging to the canonical ensemble obeys the following equation of motion [19]:…”

mentioning

confidence: 99%

“…However, here the complex function Ψ(r) carries information on both the condensed and non condensed atoms. The condensate and the thermal cloud can be split via the coarse-graining procedure [19,32]. In short, the coarse-graining allows to separate the mode characterized by the largest first order coherence length (or a coherence time) from the remaining part of the classical field.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Density fluctuations in a quasi-one-dimensional Bose gas as observed in free expansion

Gawryluk¹,

Gajda²,

Brewczyk

2015

Phys. Rev. A

Self Cite

View full text Add to dashboard Cite

We study, within a framework of the classical fields approximation, the density correlations of a weakly interacting expanding Bose gas for the whole range of temperatures across the Bose-Einstein condensation threshold. We focus on elongated quasi-one-dimensional systems where there is a huge discrepancy between the existing theory and experimental results (A. Perrin et al., Nature Phys. 8, 195 (2012)). We find that the density correlation function is not reduced for temperatures below the critical one as it is predicted for the ideal gas or for a weakly interacting system within the Bogoliubov approximation. This behavior of the density correlations agrees with the above mentioned experiment with the elongated system. Although the system was much larger then studied here we believe that the behavior of the density correlation function found there is quite generic. Our theoretical studies indicate also large density fluctuations in the trap in the quasicondensate regime where only phase fluctuations were expected. We argue that the enhanced density fluctuations can originate in the presence of interactions in the system, or more precisely in the existence of spontaneous dark solitons in the elongated gas at thermal equilibrium.Correlations are the essence of any many body systems. In particular, the quantum features of the system are manifested by some unusual correlations. The first order coherence is the basic criterion used as the definition of a Bose-Einstein condensate. And indeed, very soon after observation of trapped atomic condensates the first order coherence of such systems, manifesting itself in the ability to produce the interference fringes in a two-slit experiment, had been proven [1] experimentally. Higher order correlations leading to atom bunching were established from collisions and three-body losses [2]. Although the Glauber coherence theory introduced to characterize correlations of quantum electromagnetic field is well established now, the issue of coherence of a matter field is still under intensive investigation.A Bose-Einstein condensate is a matter wave analogue of a coherent light. A very important question is how far this analogy can be pursuit. The first difference is that atoms exist in a Fock states only: the states which are the eigenstates of the particle number operator. As a consequence, the coherent state of a matter field, understood as the exact analogue of the coherent electromagnetic field, does not exist. On the other hand, the atomic field can exhibit a higher order coherence too. The coherence ought to be understood here as the ability to produce the interference patterns not only in a single-particle detection schemes, but also in a simultaneous detection of larger number of atoms. Although the phase of a number state can be arbitrary, the Fock states can interfere in a single realization of the system [3] when no averaging over global phase is performed. Therefore higher order coherence of atomic condensates, as can be observed in a single realization of the system,...

show abstract

Classical fields approximation for bosons at nonzero temperatures

Cited by 99 publications

References 87 publications

Collapse and revival of the monopole mode of a degenerate Bose gas in an isotropic harmonic trap

Collapse and revival of the monopole mode of a degenerate Bose gas in an isotropic harmonic trap

Splitting dynamics of a two-species Bose-Einstein condensate in two translating traps

Density fluctuations in a quasi-one-dimensional Bose gas as observed in free expansion

Contact Info

Product

Resources

About