Spatial Deformation in a Phase Separated Fermi Gas

Partridge, Guthrie B.; Li, Wenhui; Liao, Yunxiang; Nguyen, Duong Thanh; Kamar, Ramsey I.; Hulet, Randall G.

doi:10.1364/ls.2006.lmc3

Cited by 53 publications

(99 citation statements)

References 3 publications

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“…A systematic and analytically accessible description of the crossover which is uniformly valid in both the normal and superfluid regime and which gives a proper account of the critical behaviour is provided by a 1/N -expansion as recently shown by Nikolić and Sachdev [15]. This method can in fact be extended in a straigthforward manner to the case of unbalanced spin populations, a subject which has attracted a lot of attention very recently [64,70].…”

Section: Discussionmentioning

confidence: 99%

Thermodynamics of the BCS-BEC crossover

et al. 2007

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We present a self-consistent theory for the thermodynamics of the BCS-BEC crossover in the normal and superfluid phase which is both conserving and gapless. It is based on the variational many-body formalism developed by Luttinger and Ward and by DeDominicis and Martin. Truncating the exact functional for the entropy to that obtained within a ladder approximation, the resulting self-consistent integral equations for the normal and anomalous Green functions are solved numerically for arbitrary coupling. The critical temperature, the equation of state and the entropy are determined as a function of the dimensionless parameter 1/kF a, which controls the crossover from the BCS-regime of extended pairs to the BEC-regime of tightly bound molecules. The tightly bound pairs turn out to be described by a Popov-type approximation for a dilute, repulsive Bose gas. Even though our approximation does not capture the critical behaviour near the continuous superfluid transition, our results provide a consistent picture for the complete crossover thermodynamics which compare well with recent numerical and field-theoretic approaches at the unitarity point.

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Section: Discussionmentioning

confidence: 99%

Thermodynamics of the BCS-BEC crossover

et al. 2007

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“…In order to make a Ginzburg-Landau expansion, order by order in powers of the ∆'s, we first integrate (26), obtaining…”

Section: The Ginzburg-landau Approximation: Derivationmentioning

confidence: 99%

“…In all these contexts, however, the gapless paired state turns out in general to suffer from a "magnetic instability": it can lower its energy by the formation of counter-propagating currents [21,22,23]. In the atomic physics context, the resolution of the instability is phase separation, into macroscopic regions of two phases in one of which standard BCS pairing occurs and in the other of which no pairing occurs [24,25,26]. In three-flavor quark matter, where the instability of the gCFL phase has been established in Refs.…”

Section: Introductionmentioning

confidence: 99%

Crystallography of three-flavor quark matter

2006

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We analyze and compare candidate crystal structures for the crystalline color superconducting phase that may arise in cold, dense but not asymptotically dense, three-flavor quark matter. We determine the gap parameter ∆ and free energy Ω(∆) for many possible crystal structures within a Ginzburg-Landau approximation, evaluating Ω(∆) to order ∆ 6 . In contrast to the two-flavor case, we find a positive ∆ 6 term and hence an Ω(∆) that is bounded from below for all the structures that we analyze. This means that we are able to evaluate ∆ and Ω as a function of the splitting between Fermi surfaces for all the structures we consider. We find two structures with particularly robust values of ∆ and the condensation energy, within a factor of two of those for the CFL phase which is known to characterize QCD at asymptotically large densities. The robustness of these phases results in their being favored over wide ranges of density. However, it also implies that the Ginzburg-Landau approximation is not quantitatively reliable. We develop qualitative insights into what makes a crystal structure favorable, and use these to winnow the possibilities. The two structures that we find to be most favorable are both built from condensates with face-centered cubic symmetry: in one case, the ud and us condensates are separately face centered cubic; in the other case ud and us combined make up a face centered cube.

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“…To shed some light on the pairing debate [7,10,11,12], we would need access to the proportionality factor linking the quantity plotted in Fig. 4 of [7] to the local pair correlation correlation function G 2 (r, r) = Ψ † ↓ (r)Ψ † ↑ (r)Ψ ↑ (r)Ψ ↓ (r) .…”

Section: Application To Experiments and Conclusionmentioning

confidence: 99%

“…However, the notion of pairing in these systems is less clear and sometimes even controversial. Recent experiments on the BEC-BCS crossover have caused a heated debate whether or not the obtained data was in agreement with pairing [7,10,11,12]. In addition, pairing without superfluidity [13] has been observed in these experiments, raising fundamental questions on quantum correlations in fermionic many-body systems.…”

Section: Introductionmentioning

confidence: 97%

Pairing in fermionic systems: A quantum-information perspective

et al. 2009

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The notion of "paired" fermions is central to important condensed matter phenomena such as superconductivity and superfluidity. While the concept is widely used and its physical meaning is clear there exists no systematic and mathematical theory of pairing which would allow to unambiguously characterize and systematically detect paired states. We propose a definition of pairing and develop methods for its detection and quantification applicable to current experimental setups. Pairing is shown to be a quantum correlation different from entanglement, giving further understanding in the structure of highly correlated quantum systems. In addition, we will show the resource character of paired states for precision metrology, proving that the BCS states allow phase measurements at the Heisenberg limit.

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Spatial Deformation in a Phase Separated Fermi Gas

Cited by 53 publications

References 3 publications

Thermodynamics of the BCS-BEC crossover

Thermodynamics of the BCS-BEC crossover

Crystallography of three-flavor quark matter

Pairing in fermionic systems: A quantum-information perspective

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