Vortices in Superfluid Fermi Gases through the BEC to BCS Crossover

We calculate the pair correlation function and the order parameter correlation function, which probe, respectively, the intra-pair and inter-pair correlations of a Fermi gas with attractive interparticle interaction, in terms of a diagrammatic approach as a function of coupling throughout the BCS-BEC crossover and of temperature, both in the superfluid and normal phase across the critical temperature Tc. Several physical quantities are obtained from this calculation, including the pair coherence and healing lengths, the Tan's contact, the crossover temperature T * below which interpair correlations begin to build up in the normal phase, and the signature for the disappearance of the underlying Fermi surface which tends to survive in spite of pairing correlations. A connection is also made with recent experimental data on the temperature dependence of the normal coherence length as extracted from the proximity effect measured in high-temperature (cuprate) superconductors.

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“…where in the last line we have made use of the BCS gap equation (11). The short-range behavior of g ↑↓ (ρ) which results from Eq.…”

Section: Bcs Cmentioning

confidence: 99%

Temperature dependence of the pair coherence and healing lengths for a fermionic superfluid throughout the BCS-BEC crossover

Palestini

Strinati

2014

Phys. Rev. B

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“…For Bose gases, the most common method is to employ the Gross-Pitaevskii (GP) equation 7,8 . Superfluid Fermi gases can however be studied by a variety of methods, the most common are: the GinzburgLandau (GL) formalism 9 , the Bogoliubov-De Gennes (BdG) theory [10][11][12][13][14][15][16] , superfluid density functional theory 17 , the density matrix renormalization group 18 and the coarse-grained BdG approximation 19 .…”

Section: Introduction: Vortices In the Bec-bcs Crossovermentioning

confidence: 99%

“…The problem with the BdG theory is however that the method is computationally fairly cumbersome. 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] .…”

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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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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“…The Bogoliubov quasiparticles (the two branches being denoted by χ ↑ and χ ↓ ) can now be introduced as 10) where u k , v k are Bogoliubov amplitudes. For the lower branch quasiparticle field, which is simply denoted by χ (i.e, χ ≡ χ ↓ ), this becomes in real space…”

Section: A2 Galilean Transformation For Quasiparticlesmentioning

confidence: 99%

“…[7] In addition, several theoretical studies have analyzed the possible new properties of vortices across a Feshbach resonance from the BCS to the BEC side. [8,9,10,11] The physics of atomic Fermi gases is also of fundamental interest beyond the standard BCS/BEC physics, owing to the new tuning flexibility in the atomic gas systems. Under the condition of density imbalance (hence mismatched Fermi surfaces) between the spin-up and -down fermions, a modulated Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) [12] superfluid phase, has long been theoretically anticipated.…”

Section: Introductionmentioning

confidence: 99%

Unconventional interaction between vortices in a polarized Fermi gas

2008

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Recently, a homogeneous superfluid state with a single gapless Fermi surface was predicted to be the ground state of an ultracold Fermi gas with spin population imbalance in the regime of molecular Bose-Einstein condensation. We study vortices in this novel state using a symmetry-based effective field theory, which captures the low-energy physics of gapless fermions and superfluid phase fluctuations. This theory is applicable to all spin-imbalanced ultracold Fermi gases in the superfluid regime, regardless of whether the original fermion pairing interaction is weak or strong. We find a remarkable, unconventional form of the interaction between vortices. The presence of gapless fermions gives rise to a spatially oscillating potential, akin to the RKKY indirect-exchange interaction in non-magnetic metals. We compare the parameters of the effective theory to the experimentally measurable quantities and further discuss the conditions for the verification of the predicted new feature. Our study opens up an interesting question as to the nature of the vortex lattice resulting from the competition between the usual repulsive logarithmic (2D Coulomb) and predominantly attractive fermion-induced interactions.

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Vortices in Superfluid Fermi Gases through the BEC to BCS Crossover

Cited by 118 publications

References 17 publications

Temperature dependence of the pair coherence and healing lengths for a fermionic superfluid throughout the BCS-BEC crossover

Temperature dependence of the pair coherence and healing lengths for a fermionic superfluid throughout the BCS-BEC crossover

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

Unconventional interaction between vortices in a polarized Fermi gas

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