Publisher's Note: Uniform spin susceptibility and spin-gap phenomenon in the BCS-BEC-crossover regime of an ultracold Fermi gas [Phys. Rev. A<b>89</b>, 033617 (2014)]

Tajima, Hiroyuki; Kashimura, Takashi; Hanai, Ryo; Watanabe, Ryota; Ōhashi, Y.

doi:10.1103/physreva.89.039905

Cited by 17 publications

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“…[42], we overcame this difficulty by employing an extended T -matrix approximation (ETMA) [77,78], which involves higher order pairing fluctuations beyond the TMA.…”

Section: Introductionmentioning

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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“…[42], we overcame this difficulty by employing an extended T -matrix approximation (ETMA) [77,78], which involves higher order pairing fluctuations beyond the TMA.…”

Section: Introductionmentioning

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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“…Theoretically, the possibility of the so-called spin-gap phenomenon has been discussed in the crossover region near the superfluid phase transition temperature T c 17,18,19,20,21 , where the spin susceptibility is anomalously suppressed by preformed spin-singlet Cooper pairs. Since preformed Cooper pairs also cause the pseudogap phenomenon 22,23,24,25,26 (where the single-particle density of states exhibits a gap-like structure even in the normal state), the spin-gap phenomenon and pseudogap phenomenon are deeply related to each other in the cold Fermi gas system.…”

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confidence: 99%

“…Since preformed Cooper pairs also cause the pseudogap phenomenon 22,23,24,25,26 (where the single-particle density of states exhibits a gap-like structure even in the normal state), the spin-gap phenomenon and pseudogap phenomenon are deeply related to each other in the cold Fermi gas system. So far, the spin susceptibility has theoretically been discussed in a uniform Fermi gas 18,19,20,21 , although a real ultracold Fermi gas is always prepared in a trap potential. In this paper, thus, taking this realistic situation into account, we study how spatially inhomogeneous pairing fluctuations affect the spin-gap phenomenon in a trapped unitary Fermi gas.…”

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confidence: 99%

“…In this paper, thus, taking this realistic situation into account, we study how spatially inhomogeneous pairing fluctuations affect the spin-gap phenomenon in a trapped unitary Fermi gas. For this purpose, we employ the extended T -matrix approximation (ETMA) developed in the uniform system 18,21 , to include effects of a harmonic trap within the local density approximation (LDA) 23,26 . In a uniform Fermi gas, it has been shown that ETMA correctly describes the BCS-BEC crossover behavior of the spin susceptibility 18,21 , which makes us expect that this strong-coupling theory is also valid for the trapped case.…”

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confidence: 99%

“…For this purpose, we employ the extended T -matrix approximation (ETMA) developed in the uniform system 18,21 , to include effects of a harmonic trap within the local density approximation (LDA) 23,26 . In a uniform Fermi gas, it has been shown that ETMA correctly describes the BCS-BEC crossover behavior of the spin susceptibility 18,21 , which makes us expect that this strong-coupling theory is also valid for the trapped case. We briefly note that the ordinary T -matrix approximation 22,25,27 , as well as the strong-coupling theory developed by Nozières and Schmitt-Rink 6,7 , are known to unphysically give negative spin susceptibility in the BCS-BEC crossover region, although these theories have successfully explained various many-body phenomena in the BCS-BEC crossover region.…”

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Spin Susceptibility and Effects of Inhomogeneous Strong Pairing Fluctuations in a Trapped Ultracold Fermi Gas

2015

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We theoretically investigate magnetic properties of a unitary Fermi gas in a harmonic trap. Including strong pairing fluctuations within the framework of an extended Tmatrix approximation (ETMA), as well as effects of a trap potential within the local density approximation (LDA), we calculate the local spin susceptibility χ(T, r) above the superfluid phase transition temperature T c . We show that the formation of preformed singlet Cooper pairs anomalously suppresses χ(T, r) in the trap center near T c . We also point out that, in the unitarity limit, the spin-gap temperature in a uniform Fermi gas can be evaluated from the observation of the spatial variation of χ(T, r). Since a real ultracold Fermi gas is always in a trap potential, our results would be useful for the study of how this spatial inhomogeneity affects thermodynamic properties of an ultracold Fermi gas in the BCS-BEC crossover region.

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Zero-Temperature Properties of a Strongly Interacting Superfluid Fermi Gas in the BCS–BEC Crossover Region

et al. 2016

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We investigate thermodynamic properties and effects of quantum fluctuations in the Bardeen-Cooper-Schrieffer (BCS)-Bose-Einstein condensation (BEC) crossover region of a superfluid Fermi gas in the low-temperature limit. Including strong-coupling corrections within the framework of an extended T -matrix approximation, we numerically compute the isothermal compressibility χ n . While quantum fluctuation effects on χ n in the strong-coupling BEC regime are explained by the quantum depletion due to a repulsive interaction between tightly bound molecules, effects of self-energy shift on the Fermi chemical potential are found to enhance χ n in the weak-coupling BCS region. We also show that the calculated χ n agrees well with the recent experiment on a 6 Li Fermi gas done from the weak-coupling region to the unitarity limit. Our result would be useful for the study of many-body quantum corrections in the BCS-BEC crossover region of a strongly interacting Fermi superfluid.

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Publisher's Note: Uniform spin susceptibility and spin-gap phenomenon in the BCS-BEC-crossover regime of an ultracold Fermi gas [Phys. Rev. A89, 033617 (2014)]

Cited by 17 publications

References 0 publications

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

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

Spin Susceptibility and Effects of Inhomogeneous Strong Pairing Fluctuations in a Trapped Ultracold Fermi Gas

Zero-Temperature Properties of a Strongly Interacting Superfluid Fermi Gas in the BCS–BEC Crossover Region

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