BCS-BEC Crossover in a Gas of Fermi Atoms with a Feshbach Resonance

Ōhashi, Y.; Griffin, Allan

doi:10.1103/physrevlett.89.130402

Cited by 461 publications

(580 citation statements)

References 14 publications

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“…Our data thus agrees with a simple Fermi liquid picture, while it is generally believed that the normal gas above T c exhibits a pseudogap in the unitary limit [159,160,155,161,162,163]. In this section we estimate the maximum pseudogap values in agreement with our observations, assuming the existence of a well-de ned dispersion relation k (i.e.…”

Section: Estimation Of the Maximum Pseudogap Amplitudesupporting

confidence: 80%

Thermodynamics of Ultracold Fermi Gases

Nascimbène

Navon

Chevy

et al. 2010

Latin America Optics and Photonics Conference

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Section: Estimation Of the Maximum Pseudogap Amplitudesupporting

confidence: 80%

Thermodynamics of Ultracold Fermi Gases

Nascimbène

Navon

Chevy

et al. 2010

Latin America Optics and Photonics Conference

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“…In the strong-coupling BEC regime, the system is well described by a Bose gas of N/2 tightly bound molecules [84][85][86], so that the difference between the ETMA and the SCTMA is not important, as far as we consider T c . Indeed, Fig.…”

Section: Superfluid Phase Transition and Effects Of Mass Imbal-ancementioning

confidence: 99%

Heteropairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with different species with different masses

Hanai

Ōhashi

2014

Phys. Rev. A

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We investigate the superfluid phase transition and single-particle excitations in the BCS (BareenCooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover regime of an ultracold Fermi gas with mass imbalance. In our recent paper [R. Hanai, et. al., Phys. Rev. A 88, 053621 (2013)we showed that an extended T -matrix approximation (ETMA) can overcome the serious problem known in the ordinary (non-self-consistent) T -matrix approximation that it unphysically gives double-valued superfluid phase transition temperature T c in the presence of mass imbalance. However, at the same time, the ETMA was also found to give the vanishing T c in the weak-coupling and highly mass-imbalanced case. In this paper, we inspect the correctness of this ETMA result, using the self-consistent T -matrix approximation (SCTMA). We show that the vanishing T c is an artifact of the ETMA, coming from an internal inconsistency of this theory. The superfluid phase transition actually always occurs, irrespective of the ratio of mass imbalance. We also apply the SCTMA to the pseudogap problem in a mass-imbalanced Fermi gas. We show that pairing fluctuations induce different pseudogap phenomena between the the light component and heavy component. We also point out that a 6 Li-40 K mixture is a useful system for the realization of a hetero pairing state, as well as for the study of component-dependent pseudogap phenomena.

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“…A strong attractive interaction can arise between fermions mediated by bosonic quasi-molecules associated with a Feshbach resonance. In this case it is stated that one has to be careful in applying pure BCS theory to a Fermi gas when the pairing interaction is very strong [35], due to fluctuations in the two-particle Cooper channel. One can also try to extend the experiments in optical lattices with bosonic constituents to fermionic atoms [36].…”

Section: Summary and Discussionmentioning

confidence: 99%

“…Close to a Feshbach resonance, the additional phenomenon of a BCS to BEC crossover is predicted for atomic Fermi gases [35]. A strong attractive interaction can arise between fermions mediated by bosonic quasi-molecules associated with a Feshbach resonance.…”

Section: Summary and Discussionmentioning

confidence: 99%

Nonlinear sigma model for a condensate composed of fermionic atoms

Mieck

2005

Physica A: Statistical Mechanics and its Applications

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A nonlinear sigma model is derived for the time development of a Bose-Einstein condensate composed of fermionic atoms. Spontaneous symmetry breaking of a Sp(2) symmetry in a coherent state path integral with anticommuting fields yields Goldstone bosons in a Sp(2)\U (2) coset space. After a Hubbard-Stratonovich transformation from the anticommuting fields to a local self-energy matrix with anomalous terms, the assumed short-ranged attractive interaction reduces this symmetry to a SO(4)\U (2) coset space with only one complex Goldstone field for the singlett pairs of fermions. This bosonic field for the anomalous term of fermions is separated in a gradient expansion from the density terms. The U (2) invariant density terms are considered as a background field or unchanged interacting Fermi sea in the spontaneous symmetry breaking of the SO(4) invariant action and appear as coefficients of correlation functions in the nonlinear sigma model for the Goldstone boson. The time development of the condensate composed of fermionic atoms results in a modified Sine-Gordon equation.

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BCS-BEC Crossover in a Gas of Fermi Atoms with a Feshbach Resonance

Cited by 461 publications

References 14 publications

Thermodynamics of Ultracold Fermi Gases

Thermodynamics of Ultracold Fermi Gases

Heteropairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with different species with different masses

Nonlinear sigma model for a condensate composed of fermionic atoms

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