Extension of the Ginzburg–Landau approach for ultracold Fermi gases below a critical temperature

Klimin, S. N.; Tempere, J.; Devreese, Jozef T.

doi:10.1016/j.physc.2014.03.030

Cited by 4 publications

(21 citation statements)

References 28 publications

(47 reference statements)

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“…The profile function f is subject to the boundary conditions f (0) = 0 and f (∞) = 1. Adding the effects of rotation and substituting the vortex structure (1) results in an effective energy given by 21 :…”

Section: The Effective Field Theory For Vorticesmentioning

confidence: 99%

“…Consequently the use of the BdG theory is mainly limited to the consideration of zero-temperature properties of single-vortex states [10][11][12] . Because of this big computational cost of the BdG theory, there is a recent interest in the development of effective field theories [20][21][22][23][24][25][26] . These effective field theories allow for a description of non-uniform excitations (e.g.…”

Section: Introduction: Vortices In the Bec-bcs Crossovermentioning

confidence: 99%

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Verification of an analytic fit for the vortex core profile in superfluid Fermi gases

Verhelst

Klimin

Tempere

2017

Physica C: Superconductivity and its Applications

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A characteristic property of superfluidity and -conductivity is the presence of quantized vortices in rotating systems. To study the BEC-BCS crossover the two most common methods are the Bogoliubov-De Gennes theory and the usage of an effective field theory. In order to simplify the calculations for one vortex, it is often assumed that the hyperbolic tangent yields a good approximation for the vortex structure. The combination of a variational vortex structure, together with cylindrical symmetry yields analytic (or numerically simple) expressions.The focus of this article is to investigate to what extent this analytic fit truly reflects the vortex structure throughout the BEC-BCS crossover at finite temperatures. The vortex structure will be determined using the effective field theory presented in [Eur. Phys. Journal B 88, 122 (2015)] and compared to the variational analytic solution. By doing this it is possible to see where these two structures agree, and where they differ. This comparison results in a range of applicability where the hyperbolic tangent will be a good fit for the vortex structure.1 arXiv:1603.02523v1 [cond-mat.quant-gas]

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Section: The Effective Field Theory For Vorticesmentioning

confidence: 99%

Section: Introduction: Vortices In the Bec-bcs Crossovermentioning

confidence: 99%

Verification of an analytic fit for the vortex core profile in superfluid Fermi gases

Verhelst

Klimin

Tempere

2017

Physica C: Superconductivity and its Applications

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“…[34] and [35]. The description of a Fermi gas with s-wave pairing within this formalism is performed using the effective bosonic action for the pair field (r,τ ) (the macroscopic order parameter).…”

Section: Field Equationsmentioning

confidence: 99%

“…There are extensions of the GL approach to lower temperatures based on expanding the free energy in powers of the small parameter η ≡ 1 − T /T c [27][28][29][30] or using a microscopic treatment [31][32][33]. Our recent investigation [34,35], focused on atomic Fermi gases in the BCS-BEC crossover regime, has been devoted to the development of an effective method for the description of the macroscopic wave function of a fermionic superfluid system without assuming η small. In Refs.…”

Section: Introductionmentioning

confidence: 99%

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Finite-temperature effective field theory for dark solitons in superfluid Fermi gases

2014

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We use a finite-temperature effective field theory recently developed for superfluid Fermi gases to investigate the properties of dark solitons in these superfluids. Our approach provides an analytic solution for the dip in the order parameter and the phase profile across the soliton, which can be compared with results obtained in the framework of the Bogoliubov-de Gennes equations. We present results in the whole range of the BCS-BEC crossover, for arbitrary temperatures and taking into account Gaussian fluctuations about the saddle point. The obtained analytic solutions yield an exact energy-momentum relation for a dark soliton showing that the soliton in a Fermi gas behaves like a classical particle even at nonzero temperatures. The spatial profile of the pair field and for the parameters of state for the soliton are analytically studied.

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Diversified vortex phase diagram for a rotating trapped two-band Fermi gas in the BCS-BEC crossover

2018

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We report the equilibrium vortex phase diagram of a rotating two-band Fermi gas confined to a cylindrically symmetric parabolic trapping potential, using the recently developed finite-temperature effective field theory (Klimin et al 2016 Phys. Rev. A 94 023620). A non-monotonic resonant dependence of the free energy as a function of the temperature and the rotation frequency is revealed for a two-band superfluid. We particularly focus on novel features that appear as a result of interband interactions and can be experimentally resolved. The resonant dependence of the free energy is directly manifested in vortex phase diagrams, where areas of stability for both integer and fractional vortex states are found. The study embraces the BCS-BEC crossover regime and the entire temperature range below the critical temperature T c . Significantly different behavior of vortex matter as a function of the interband coupling is revealed in the BCS and BEC regimes. regime has also attracted much attention [27]. Vortex states in multiband quantum atomic gases have been studied to a far lesser extent.Therefore, in this work, the subject of our interest are fractional vortices in two-band Fermi gases of ultracold atoms in the BCS-BEC crossover. Although there is some similarity between superconductors and condensed atomic Fermi gases, the analogy is not complete. For one difference, cold gases certainly require an independent treatment by specific methods suitable in the entire BCS-BEC crossover range.Recently, the stability of different vortex states in a rotating trapped one-band Fermi gas has been theoretically studied in [14,15] using, respectively, the coarse-grained Bogoliubov-de Gennes (BdG) theory [28] (first applied to atomic Fermi gases in [29]) and the recently developed finite-temperature effective field theory (EFT) [30,31]. The finite-temperature EFT results agree with the results of the BdG theory and experiment for different manifestations: collective excitations and vortices [15,31], and solitons [32,33]. The finitetemperature EFT is aimed to find analytic results whenever possible. For example, for dark solitons in condensed Fermi gases, the finite-temperature EFT provides exact analytic solutions of the soliton equation of motion [32], while the BdG equations for the same problem have been solved only numerically.Besides our studies, there are several modifications of the EFT of condensed Fermi gases described in different publications and related to different ranges of external parameters (e.g., temperature and scattering length). They are developed either for the close vicinity to the critical temperature [34] or for the case T=0 (e.g., [35][36][37]). As analyzed in [31], the present finite-temperature EFT agrees with preceding works in all these limiting cases.At present, experimental data on vortices in two-band superfluid atomic Fermi gases are still lacking, in spite of the expected new physics stemming from the interband interactions in such a system. We report the first such theoretical study, to pave ...

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Extension of the Ginzburg–Landau approach for ultracold Fermi gases below a critical temperature

Cited by 4 publications

References 28 publications

Verification of an analytic fit for the vortex core profile in superfluid Fermi gases

Verification of an analytic fit for the vortex core profile in superfluid Fermi gases

Finite-temperature effective field theory for dark solitons in superfluid Fermi gases

Diversified vortex phase diagram for a rotating trapped two-band Fermi gas in the BCS-BEC crossover

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