Role of fourth-order phase-space moments in collective modes of trapped Fermi gases

Chiacchiera, Silvia; Lepers, Thomas; Davesne, D.; Urban, Michael

doi:10.1103/physreva.84.043634

Cited by 18 publications

(37 citation statements)

References 20 publications

(77 reference statements)

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“…Better agreement could also be obtained by solving the Boltzmann equation approximately by taking moments with basis functions for δf σ [23,26,28]. Such an approach has indeed been successful in describing the frequency and damping of collective modes in 3D.…”

Section: Methodsmentioning

confidence: 94%

Shear viscosity and spin-diffusion coefficient of a two-dimensional Fermi gas

Bruun¹

2012

Phys. Rev. A

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Using kinetic theory, we calculate the shear viscosity and the spin-diffusion coefficient as well as the associated relaxation times for a two-component Fermi gas in two dimensions, as a function of temperature, coupling strength, polarization, and mass ratio of the two components. It is demonstrated that the minimum value of the viscosity decreases with the mass ratio, since Fermi blocking becomes less efficient. We furthermore analyze recent experimental results for the quadrupole mode of a two-dimensional gas in terms of viscous damping, obtaining a qualitative agreement using no fitting parameters.

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Section: Methodsmentioning

confidence: 94%

Shear viscosity and spin-diffusion coefficient of a two-dimensional Fermi gas

Bruun¹

2012

Phys. Rev. A

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“…The same argument should also apply to the radial quadrupole and scissors modes not studied in the present paper. One should therefore be careful when comparing theoretical results obtained for a harmonic trap with experimental ones (as done in [7,15,18]), since the anharmonicity effects cannot be completely absorbed in a renormalized radial trap frequency.…”

Section: Discussionmentioning

confidence: 99%

“…[18], we are looking for a semi-analytical solution of the Boltzmann equation (4) by using the method of phase-space moments. In this section, we will generalize the formalism of that paper to the case of an arbitrary trap potential V T and with mean field U .…”

Section: B Moments Methodsmentioning

confidence: 99%

“…[18], when the moments method is extended to higher order, there can be many eigenvalues belonging to a single collective mode. In this case, the scattering of the eigenvalues, which goes over into a continuous spectrum in the limit of an infinite number of moments [20], corresponds to a new contribution to the damping (Landau damping) in addition to the imaginary parts coming from the collision term.…”

Section: Eigenmodes and Response Functionmentioning

confidence: 99%

“…[18], we will extend the ansatz (23) by including higher-order terms. At the next higher order, the ansatz contains 18 terms where:…”

Section: Sloshing Mode At Third Order a Extended Ansatzmentioning

confidence: 99%

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Trap anharmonicity and sloshing mode of a Fermi gas

et al. 2012

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For a gas trapped in a harmonic potential, the sloshing (or Kohn) mode is undamped and its frequency coincides with the trap frequency, independently of the statistics, interaction and temperature of the gas. However, experimental trap potentials have usually Gaussian shape and anharmonicity effects appear as the temperature and, in the case of Fermions, the filling of the trap are increased. We study the sloshing mode of a degenerate Fermi gas in an anharmonic trap within the Boltzmann equation, including in-medium effects in both the transport and collision terms. The calculated frequency shifts and damping rates of the sloshing mode due to the trap anharmonicity are in satisfactory agreement with the available experimental data. We also discuss higher-order dipole, octupole, and bending modes and show that the damping of the sloshing mode is caused by its coupling to these modes.

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The BCS–BEC crossover: From ultra-cold Fermi gases to nuclear systems

et al. 2018

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This report adresses topics and questions of common interest in the fields of ultra-cold gases and nuclear physics in the context of the BCS-BEC crossover. By this crossover, the phenomena of Bardeen-Cooper-Schrieffer (BCS) superfluidity and Bose-Einstein condensation (BEC), which share the same kind of spontaneous symmetry breaking, are smoothly connected through the progressive reduction of the size of the fermion pairs involved as the fundamental entities in both phenomena. This size ranges, from large values when Cooper pairs are strongly overlapping in the BCS limit of a weak inter-particle attraction, to small values when composite bosons are non-overlapping in the BEC limit of a strong inter-particle attraction, across the intermediate unitarity limit where the size of the pairs is comparable with the average inter-particle distance.The BCS-BEC crossover has recently been realized experimentally, and essentially in all of its aspects, with ultracold Fermi gases. This realization, in turn, has raised the interest of the nuclear physics community in the crossover problem, since it represents an unprecedented tool to test fundamental and unanswered questions of nuclear manybody theory. Here, we focus on the several aspects of the BCS-BEC crossover, which are of broad joint interest to both ultra-cold Fermi gases and nuclear matter, and which will likely help to solve in the future some open problems in nuclear physics (concerning, for instance, neutron stars). Similarities and differences occurring in ultra-cold Fermi gases and nuclear matter will then be emphasized, not only about the relative phenomenologies but also about the theoretical approaches to be used in the two contexts. Common to both contexts is the fact that at zero temperature the BCS-BEC crossover can be described at the mean-field level with reasonable accuracy. At finite temperature, on the other hand, inclusion of pairing fluctuations beyond mean field represents an essential ingredient of the theory, especially in the normal phase where they account for precursor pairing effects.After an introduction to present the key concepts of the BCS-BEC crossover, this report discusses the mean-field treatment of the superfluid phase, both for homogeneous and inhomogeneous systems, as well as for symmetric (spinor isospin-balanced) and asymmetric (spin-or isospin-imbalanced) matter. Pairing fluctuations in the normal phase are then considered, with their manifestations in thermodynamic and dynamic quantities. The last two Sections provide a more specialized discussion of the BCS-BEC crossover in ultra-cold Fermi gases and nuclear matter, respectively. The separate discussion in the two contexts aims at cross communicating to both communities topics and aspects which, albeit arising in one of the two fields, share a strong common interest.

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Role of fourth-order phase-space moments in collective modes of trapped Fermi gases

Cited by 18 publications

References 20 publications

Shear viscosity and spin-diffusion coefficient of a two-dimensional Fermi gas

Shear viscosity and spin-diffusion coefficient of a two-dimensional Fermi gas

Trap anharmonicity and sloshing mode of a Fermi gas

The BCS–BEC crossover: From ultra-cold Fermi gases to nuclear systems

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