Probing two-fluid hydrodynamics in a trapped Fermi superfluid at unitarity

Taylor, Edward; Hu, Hui; Liu, Xia-Ji; Griffin, Allan

doi:10.48550/arxiv.0709.0698

Cited by 5 publications

(10 citation statements)

References 15 publications

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“…They studied the dipole mode of two component trapped gases as a function of a collision rate in some situations [20,21], and the crossover between zero and first sound modes in the cigar-shaped trap [22,23]. Recently, collective excitations in the unitarity limit were studied [24,25,26].…”

Section: Introductionmentioning

confidence: 99%

Zero and First Sound in Normal Fermi Systems

2009

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On the basis of a moment method, general solutions of a linearized Boltzmann equation for a normal Fermi system are investigated. In particular, we study the sound velocities and damping rates as functions of the temperature and the coupling constant. In the extreme limits of collisionless and hydrodynamic regimes, eigenfrequency of sound mode obtained from the moment equations reproduces the well-known results of zero sound and first sound. In addition, the moment method can describe crossover between those extreme limits at finite temperatures. Solutions of the moment equations also involve a thermal diffusion mode. From solutions of these equations, we discuss excitation spectra corresponding to the particle-hole continuum as well as collective excitations. We also discuss a collective mode in a weak coupling case.Comment: 38 pages, 5 figure

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Section: Introductionmentioning

confidence: 99%

Zero and First Sound in Normal Fermi Systems

2009

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“…The result of Ref. [9] showed that the weight of first sound is everywhere much larger than second sound. Second sound is only weakly coupled into the density response function (Z 2 ≃ 0.05 is the maximum at T ≃ 0.9T c ).…”

Section: Linear Response Solution Of Landau's Two-fluid Equationsmentioning

confidence: 98%

“…The density response spectrum χ ′′ nn (q, ω) in a superfluid Fermi gas at unitarity was calculated in Ref. [9]. The result of Ref.…”

Section: Linear Response Solution Of Landau's Two-fluid Equationsmentioning

confidence: 99%

“…[6][7][8]. References [8][9][10][11] studied out-of-phase collective modes in trapped Fermi gases, which are more relevant to experiments. However, out-of-phase modes have not been observed experimentally so far.…”

Section: Introductionmentioning

confidence: 99%

“…Reference [6] also argued that both sound modes can be excited and detected both as density and thermal waves, but the quantitative results were not presented. Reference [9] calculated the two-fluid density response spectrum in a uniform superfluid gas of Fermi atoms in the unitary limit, and showed that second sound is only weakly coupled into density response [9]. At first sight, this result seems to imply that the second sound cannot be excited by a density perturbation.…”

Section: Introductionmentioning

confidence: 99%

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Propagation of second sound in a superfluid Fermi gas in the unitary limit

Arahata

Nikuni

2009

Phys. Rev. A

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Erratum: Propagation of Second sound in a superfluid Fermi gas in the unitary limit [Phys. Rev. A 80, 043613 (2009)] Emiko Arahata and Tetsuro NikuniWe made some errors in Sec. IV. The correct interaction parameter is g B n B /k B T c = 0.807. The sound velocities plotted in Fig. 7 are normalized by the "Fermi velocity" defined in terms of the density and mass of bosons, i.e. v f = (6π 2 n B ) 1/3 /2M . Due to mishandling of raw data, the values given in Fig. 8 did not correspond to our calculated results. The corrected version of the figure is given as Fig. 0 below. The qualitative behaviors of W 1 and W 2 in the BEC limit are quite different from those in the unitary limit, i.e. W 2 > W 1 in most temperatures (T > 0.4T c ). This change does not affect any other result nor the conclusion of the paper. FIG. 0: W1/(W1 + W2) and W2/(W1 + W2) as a function of temperature.We study sound propagation in a uniform superfluid gas of Fermi atoms in the unitary limit.The existence of normal and superfluid components leads to appearance of two sound modes in the collisional regime, referred to as first and second sound. The second sound is of particular interest as it is a clear signal of a superfluid component. Using Landau's two-fluid hydrodynamic theory, we calculate hydrodynamic sound velocities and these weights in the density response function. The latter is used to calculate the response to a sudden modification of the external potential generating pulse propagation. The amplitude of a pulse which is proportional to the weight in the response function, is calculated the basis of the approach of Nozières and Schmitt-Rink (NSR) for the BCS-BEC crossover. We show that, in a superfluid Fermi gas at unitarity, the second sound pulse is excited with an appreciate amplitude by density perturbations.

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Density profiles and density oscillations of an interacting three-component normal Fermi gas

Silva¹

2010

J. Phys. B: At. Mol. Opt. Phys.

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We use a semiclassical approximation to investigate density variations and dipole oscillations of an interacting three-component normal Fermi gas in a harmonic trap. We consider both attractive and repulsive interactions between different pairs of fermions and study the effect of population imbalance on densities. We find that the density profiles significantly deviate from those of noninteracting profiles and extremely sensitive to interactions and population imbalance. Unlike for a two-component Fermi system, we find density imbalance even for balanced populations. For some range of parameters, one component completely repels from the trap center giving rise a donut shape density profile. Further, we find that the in-phase dipole oscillation frequency is consistent with Kohn's theorem and other two dipole mode frequencies are strongly effected by the interactions and the number of atoms in the harmonic trap.

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Probing two-fluid hydrodynamics in a trapped Fermi superfluid at unitarity

Cited by 5 publications

References 15 publications

Zero and First Sound in Normal Fermi Systems

Zero and First Sound in Normal Fermi Systems

Propagation of second sound in a superfluid Fermi gas in the unitary limit

Density profiles and density oscillations of an interacting three-component normal Fermi gas

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