Collective modes of trapped Fermi gases with in-medium interaction

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

doi:10.1103/physreva.79.033613

Cited by 25 publications

(85 citation statements)

References 40 publications

(108 reference statements)

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“…3 of Ref. [15]. For the study of collective oscillations, it is sufficient to consider small deviations from equilibrium and to linearize the Boltzmann equation with respect to δf = f − f eq .…”

Section: A Linearized Boltzmann Equation With In-medium Effectsmentioning

confidence: 99%

“…Note that, especially near the critical temperature, the in-medium cross-section dσ/dΩ can differ strongly from the free one [7,15,16].…”

Section: A Linearized Boltzmann Equation With In-medium Effectsmentioning

confidence: 99%

“…The trap was loaded with N = 6 × 10 5 atoms of 6 Li in the unitary limit, 1/(k F a) = 0, and the temperature was varied between ∼ 0 and 1.2T F . Since we cannot describe the superfluid phase, we limit ourselves to temperatures above 0.3T F [15]. Moreover, we approximate the unitary limit numerically by setting 1/(k F a) = −0.01.…”

Section: Realistic Trap Potentialmentioning

confidence: 99%

“…The framework of our study is the Boltzmann equation, including mean field [15] and in-medium crosssection [7,15,16]. Especially the mean field is expected to be important in the present context, because it can have a sizable effect on the density profile, i.e., on how far the cloud extends into the anharmonic region of the trap potential.…”

Section: Introductionmentioning

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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Section: A Linearized Boltzmann Equation With In-medium Effectsmentioning

confidence: 99%

“…Note that, especially near the critical temperature, the in-medium cross-section dσ/dΩ can differ strongly from the free one [7,15,16].…”

Section: A Linearized Boltzmann Equation With In-medium Effectsmentioning

confidence: 99%

Section: Realistic Trap Potentialmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Trap anharmonicity and sloshing mode of a Fermi gas

et al. 2012

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“…In the normal phase, the transition between hydrodynamic and collisionless regimes can be described by the Boltzmann equation [2,[12][13][14][15][16][17][18]. The test-particle method for the numerical solution of the Boltzmann equation has been used for many years in the field of heavy-ion collisions [19] and more recently also for ultracold atoms [12,16,[20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Numerical solution of the Boltzmann equation for trapped Fermi gases with in-medium effects

2015

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Using the test-particle method, we solve numerically the Boltzmann equation for an ultra-cold gas of trapped fermions with realistic particle number and trap geometry in the normal phase. We include a mean-field potential and in-medium modifications of the cross-section obtained within a T matrix formalism. After some tests showing the reliability of our procedure, we apply the method to realistic cases of practical interest, namely the anisotropic expansion of the cloud and the radial quadrupole mode oscillation. Our results are in good agreement with experimental data. Although the in-medium effects significantly increase the collision rate, we find that they have only a moderate effect on the anisotropic expansion and on frequency and damping rate of the quadrupole mode.

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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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Collective modes of trapped Fermi gases with in-medium interaction

Cited by 25 publications

References 40 publications

Trap anharmonicity and sloshing mode of a Fermi gas

Trap anharmonicity and sloshing mode of a Fermi gas

Numerical solution of the Boltzmann equation for trapped Fermi gases with in-medium effects

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

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