Finite temperature correction to the Thomas–Fermi approximation for a Bose–Einstein condensate: comparison between theory and experiment

Caracanhas, M. A.; Seman, J. A.; Ramos, E. R. F.; Henn, E. A. L.; Magalhães, K. M. F.; Helmerson, Kristian; Bagnato, Vanderlei Salvador

doi:10.1088/0953-4075/42/14/145304

Cited by 16 publications

(24 citation statements)

References 18 publications

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“…There is an agreement with Castin-Dum predictions [9] for low temperatures, however, when the temperature gets higher the ratioR 5 /N 0 departs from the Castin-Dum value getting larger (see Fig. 4 of [12]). The authors explain this behavior by us- ing a combination of a modified Hartree-Fock model to describe the condensed and thermal fractions in a trap and an expansion model formulated by Castin and Dum [9].…”

supporting

confidence: 83%

Free expansion of a Bose–Einstein condensate in the presence of a thermal cloud

Gawryluk¹,

Brewczyk²,

Gajda³

et al. 2010

J. Phys. B: At. Mol. Opt. Phys.

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We investigate numerically the free-fall expansion of a 87 Rb atoms condensate at nonzero temperatures. The classical field approximation is used to separate the condensate and the thermal cloud during the expansion. We calculate the radial and axial widths of the expanding condensate and find clear evidence that the thermal component changes the dynamics of the condensate. Our results are confronted against the experimental data.

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supporting

confidence: 83%

Free expansion of a Bose–Einstein condensate in the presence of a thermal cloud

Gawryluk¹,

Brewczyk²,

Gajda³

et al. 2010

J. Phys. B: At. Mol. Opt. Phys.

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“…the integrated value of the anomalous density[22]. The relation (11.a) reproduces the overall behavior observed experimentally in[61] as well as yielding the zero temperature expression for 1 both theoretical treatments of HFB-Popov and experimental results of[61] for small values of β .Furthermore, despite the lack of experimental data of the anomalous density in the literature, we can point out from expression (11.b) that the radius of the anomalous density is small compared to that of the condensate at low temperature. At high temperature both radii should vanish since 0 the condensed fraction.…”

supporting

confidence: 75%

Collective modes and generation of a new vortex in a trapped Bose gas at finite temperature

Boudjemâa

2013

Phys. Rev. A

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The dynamics of Bose-Einstein condensate (BEC) is studied at nonzero temperatures using our variational time-dependent-HFB formalism. We have shown that this approach is an efficient tool to study the expansion and collective excitations of the condensate, the thermal cloud and the anomalous correlation function at nonzero temperatures. We have found that the condensate and the anomalous density have the same breathing oscillations. We have investigated, on the other hand, the behavior of a single quantized vortex in a harmonically trapped BEC at nonzero temperatures. Generalized expressions for vortex excitations, vortex core size and Kelvin modes have been derived. An important and somehow surprising result is that the numerical solution of our equations predicts that the vortex core is partially filled by the thermal atoms at nonzero temperatures. We have shown that the effect of thermal fluctuations is important and it may lead to enhancing the size of the vortex core. The behavior of the singly anomalous vortex has also been studied at nonzero temperatures.

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“…To give an example, we can mention the theory of an expanding Bose gas at finite temperatures proposed in [2]. Comparison of the theory [2] with three experimental studies of an expanding two-component gas [3][4][5] revealed contradictions between the experimental and theoretical results.The comment also contains a number of statements that are difficult to agree with. The authors of the comment erroneously believe that our estimate of the accuracy (1.8%) refers to the description of expansion of the condensed fraction in a two-component Bose gas.…”

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confidence: 99%

mentioning

confidence: 99%

Response to the comment on “Interaction of two fractions in a degenerate Bose gas at finite temperatures” (JETP Lett. 103, 403 (2016))

et al. 2016

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The importance of studying the effects of interaction between the condensed and uncondensed fractions in a degenerate Bose gas was pointed out in the comment on our work [1]. We agree and mentioned the importance of such investigations ourselves.The authors of the comment point out that the analysis of the experimental data should be conducted on the basis of a more complete theoretical model. The bibliography of such theoretical models was presented in [1]. However, the theoretical description of the expansion of a two-component Bose gas seems to be a very complicated problem. To give an example, we can mention the theory of an expanding Bose gas at finite temperatures proposed in [2]. Comparison of the theory [2] with three experimental studies of an expanding two-component gas [3][4][5] revealed contradictions between the experimental and theoretical results.The comment also contains a number of statements that are difficult to agree with. The authors of the comment erroneously believe that our estimate of the accuracy (1.8%) refers to the description of expansion of the condensed fraction in a two-component Bose gas. Our analysis consists in comparing the observed characteristics of two-component Bose gases with the Gross-Pitaevskii theory for pure condensates. In [1], the expansion of the pure condensed fraction was calculated, the accuracy of such calculations was estimated, comparison with the experiment was carried out, and quantitative conclusions about the interaction of two fractions were drawn.It is worth mentioning that in [1] we solved the time-dependent Gross-Pitaevskii equation rather than the time-independent one, as the authors of the comment assume. The authors of the comment point out that, for the analysis of our experimental data, "much more useful would be the calculation of the steady-state density distributions of the normal and condensed phases by Eqs. (1)-(3)." However, the authors of the comment do not make any difference between the time-independent and time-dependent problems and it remains absolutely unclear how one should analyze the expansion of atoms, which is a time-dependent problem, on the basis of the calculation of steady-state distributions.The authors of the comment point out that "such calculations were carried out many times and give much better agreement with the experiment (see, e.g.[6])." We could not find in [6] a solution of the timedependent problem of the expansion of a two-component gas we are interested in.

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Finite temperature correction to the Thomas–Fermi approximation for a Bose–Einstein condensate: comparison between theory and experiment

Cited by 16 publications

References 18 publications

Free expansion of a Bose–Einstein condensate in the presence of a thermal cloud

Free expansion of a Bose–Einstein condensate in the presence of a thermal cloud

Collective modes and generation of a new vortex in a trapped Bose gas at finite temperature

Response to the comment on “Interaction of two fractions in a degenerate Bose gas at finite temperatures” (JETP Lett. 103, 403 (2016))

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