Interference patterns of superfluid Fermi gases in the BCS-BEC crossover released from optical lattices

We study the formation and dynamics of shock waves initiated by a repulsive potential in a superfluid unitary Fermi gas by using the order-parameter equation. In the theoretical framework, the regularization process of shock waves mediated by the quantum pressure term is purely dispersive. Our results show good agreement with the experiment of Joseph et al. [Phys. Rev. Lett. 106, 150401 (2011)]. We reveal that the boxlike-shaped density peak observed in the experiment consists of many vortex rings due to the transverse instability of the dispersive shock wave. In addition, we study the transition from a sound wave to subsonic shock waves by increasing the strength of the repulsive potential and show a strong qualitative change in the propagation speed of the wavefronts. In the relatively small strength regime, the speed decreases below the sound speed with increasing the strength as a scaling behavior, while in the large regime the speed remains almost unchanged, which is found to be the same expansion speed of the proliferation of the vortex rings.

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“…The dynamic behaviors of Fermi superfluids can be described by the following time dependent order-parameter equation [32][33][34][35][36] …”

Section: A Theoretical Descriptionmentioning

confidence: 99%

Dynamics of shock waves in a superfluid unitary Fermi gas

Wen

Shui

Shan

et al. 2015

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

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“…In Eq. (1), we assume the power-law form of the equation of state as µ(n) = C|ψ| 2γ , which is being used successfully to study the Fermi superfluid along the crossover [7,8,[19][20][21][22][23][24][25]27]. Here, C is a constant depending on the atom's interaction strength [22,23] and γ is a function of an interaction parameter η = 1/k F a [22,23], where k F is the Fermi wave vector and a is the scattering length between Fermi atoms of different components.…”

Section: The Modelmentioning

confidence: 99%

Bloch band and Bloch waves of superfluid Fermi gases in optical lattices

Wei

Xue

2010

Phys. Rev. A

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Bloch band and stabilities of Bloch waves of superfluid Fermi gases in one-dimensional (1D) periodic optical lattices are discussed. Within the hydrodynamical theory and the two-mode approximation, the Bloch band structure, the energetic and dynamical instabilities of Bloch waves at the first Brilliouin zone are presented. The results show that, when the atom density is beyond a critical value, a loop structure in the Bloch band at the zone edge is developed along the BEC-BCS crossover. The Bloch band structure and the stabilities of Bloch waves are modified dramatically when the system crosses from the BEC side to the BCS side, and they can be adjusted to the required characteristics by changing the atom's interaction (with the Feshbach resonance technique), the atom density, and the lattice parameters. The analytical expressions of the critical atom density for exciting the loop structure and maintaining the stabilities of Bloch waves are obtained.

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“…In this work, we simulate the ENS experiment for the dipole oscillations of the Bose-Fermi superfluid mixtures by carrying out an extensive numerical simulation for coupled cylindrically-symmetric orderparameter equations. The coupled time-dependent order-parameter equations [36,37] are formulated with Gross-Pitaevskii equation [38,39] for Bose superfluids and the order-parameter equation [40][41][42] with the equation of state fitting from the experimental data [43] for Fermi superfluids in the BCS-BEC crossover.…”

Section: Introductionmentioning

confidence: 99%

Collective dipole oscillations in a mixture of Bose and Fermi superfluids in the BCS–BEC crossover

Wen

2018

New J. Phys.

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We present a study for the collective dipole oscillations of a mixture of Bose and Fermi superfluids in the crossover from Bardeen-Cooper-Schrieffer (BCS) superfluid to a molecular Bose-Einstein condensate (BEC) in the ENS experimental setup (Ferrier-Barbut et al 2014 Science 345 1035). The dynamics of the double superfluidity is described by coupled time-dependent order-parameter equations, which are Gross-Pitaevskii equations for the Bose superfluid, coupled to the orderparameter equation including the equation of state fitting from the experimental data for the Fermi superfluid in the BCS-BEC crossover. The numerical simulations show that due to the boson-fermion interaction, the frequencies of the dipole oscillations of the Bose and Fermi superfluids are both downshifted and the frequency shifts increase monotonically from the BCS side to BEC side, which are in agreement with the experiment. We further study the dependencies of the frequency shifts on the oscillation amplitudes and the nonlinear effects, in which the Bose and Fermi superfliuds show different features. The frequency shifts of the Bose superfluid increase linearly as the oscillation amplitudes increase, while the frequency shifts of the Fermi superfluid show a quadratical increase. It is found that the intrinsic dipole oscillations of the Bose (Fermi) superfluid can be triggered by only boosting the Fermi (Bose) superfluid.

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Interference patterns of superfluid Fermi gases in the BCS-BEC crossover released from optical lattices

Cited by 27 publications

References 37 publications

Dynamics of shock waves in a superfluid unitary Fermi gas

Dynamics of shock waves in a superfluid unitary Fermi gas

Bloch band and Bloch waves of superfluid Fermi gases in optical lattices

Collective dipole oscillations in a mixture of Bose and Fermi superfluids in the BCS–BEC crossover

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