Collective dipole oscillations of a spin-orbit coupled Fermi gas

Zhang, Shanchao; He, Chengdong; Hajiyev, Elnur; Ren, Zejian; Song, Bo

doi:10.1038/s41598-018-36337-9

Cited by 8 publications

(10 citation statements)

References 35 publications

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“…The successful experimental realization of the synthetic coupling between atomic (pseudo) spin and momentum is another important progress in cold atomic gases [53][54][55][56][57][58][59]. This synthetic coupling is so-called spin-orbit coupling (SOC).…”

Section: Introductionmentioning

confidence: 99%

Large-momentum tail of one-dimensional Fermi gases with spin-orbit coupling

2020

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We study the contacts, large-momentum tail, radio-frequency spectroscopy, and some other universal relations for an ultracold one-dimensional (1D) two-component Fermi gas with spin-orbit coupling (SOC). Different from previous studies, we find that the q −8 tail in the spin-mixing (off-diagonal) terms of the momentum distribution matrix is dependent on the two SOC parameters in the laboratory frame for 1D systems, where q is the relative momentum. This tail can be observed through time-of-flight measurement as a direct manifestation of the SOC effects on the many-body level. Besides the traditional 1D even-wave scattering length, we find that two new physical quantities must be introduced due to the SOC. Consequently, two new adiabatic energy relations with respect to the two SOC parameters are obtained. Furthermore, we derive the pressure relation and virial theorem at short distances for this system. To find how the SOC modifies the large-momentum behavior, we take the SOC parameters as perturbations since the strength of the SOC should be much smaller than the corresponding strength scale of the interatomic interactions. In addition, by using the operator product expansion method, we derive the asymptotic behavior of the large-momentum distribution matrix up to the q −8 order and find that the diagonal terms of the distribution matrix include the contact of traditional 1D even-wave scattering length as the leading term and the SOC modified terms beyond the leading term, the off-diagonal term is beyond the subleading term and is corrected by the SOC parameters. We also find that the momentum distribution matrix shows spin-dependent and anisotropic features. Furthermore, we calculate the momentum distribution matrix in the laboratory frame for the experimental implication. In addition, we calculate the high-frequency tail of the radio-frequency spectroscopy and find that the presence of the contact related to the center-of-mass momentum in the radio-frequency spectral is due to the SOC effects. This paper paves the way for exploring the profound properties of many-body quantum systems with SOC in one dimension.

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Section: Introductionmentioning

confidence: 99%

Large-momentum tail of one-dimensional Fermi gases with spin-orbit coupling

2020

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“…Collective excitations that characterize a system's response to small perturbations constitute one of the main sources of information for understanding the physics of many-body systems [19,20]. In the last two decades, collective modes have been extensively investigated to understand the properties of atomic gases in various systems [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38], including bosons [39,40], fermions [41,42], and multi-components, such as spin-orbitcoupled bosons [43] and fermions [44], Bose-Bose mixtures [45] and degenerate Bose-Fermi mixtures [46,47].…”

Section: Introductionmentioning

confidence: 99%

Collective oscillation modes of a superfluid Bose–Fermi mixture

Wen

Wang

2019

New J. Phys.

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In this work, we present a theoretical study for the collective oscillation modes, i.e. quadrupole, radial and axial mode, of a mixture of Bose and Fermi superfluids in the crossover from a Bardeen-Cooper-Schrieffer (BCS) superfluid to a molecular Bose-Einstein condensate (BEC) in harmonic trapping potentials with cylindrical symmetry of experimental interest. To this end, we start from the coupled superfluid hydrodynamic equations for the dynamics of Bose-Fermi superfluid mixtures and use the scaling theory that has been developed for a coupled system. The collective oscillation modes of Bose-Fermi superfluid mixtures are found to crucially depend on the overlap integrals of the spatial derivations of density profiles of the Bose and Fermi superfluids at equilibrium. We not only present the explicit expressions for the overlap density integrals, as well as the frequencies of the collective modes provided that the effective Bose-Fermi coupling is weak, but also test the valid regimes of the analytical approximations by numerical calculations in realistic experimental conditions. In the presence of a repulsive Bose-Fermi interaction, we find that the frequencies of the three collective modes of the Bose and Fermi superfluids are all upshifted, and the change speeds of the frequency shifts in the BCS-BEC crossover can characterize the different groundstate phases of the Bose-Fermi superfluid mixtures for different trap geometries. superfluid mixtures of 7 Li-6 Li [1, 2], 41 K-6 Li [6], and 174 Yb-6 Li [5], and the Bose-Fermi interaction gives rise to a rich behavior. In the presence of a repulsive Bose-Fermi interaction, the frequencies of the dipole oscillations of the Bose and Fermi superfluids are both downshifted in the weakly confined direction [1,5,6], and the frequency shifts increase monotonically from the BCS side to the BEC side [48,49]. In contrast, the frequency in the tight confinement for the Bose superfluid is upshifted, whereas the frequency for the Fermi superfluid is still downshifted [6]. The frequency shifts show non-monotonic and resonantlike behaviors in both directions around the BCS side [6], which may be originated from the effects of fermionic pairs breaking [50].It is naturally to ask how Bose-Fermi interaction affects the collective modes of Bose and Fermi superfluids in the BCS-BEC crossover, which is of great interest recently. However, a theoretical study for the collective oscillation modes of Bose-Fermi superfluid mixtures in a realistic experimental situation is highly nontrivial. In this work, to study quadrupole, radial and axial modes in cylindrically symmetric traps, we start from the coupled superfluid hydrodynamic equations describing the dynamics of the Bose-Fermi superfluid mixtures. The scaling method for coupled systems is then applied, and the eigenvalue equations for the coupled collective modes are obtained, which are crucially sensitive to the overlap integrals of the spatial derivations of the Bose and Fermi densities at groundstate. To present the explicit expressio...

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“…For a two-component BEC, experimentally realizable one-dimensional spin-orbit coupling [1,9] gives rise to an energy-quasimomentum dispersion relation featuring two energy bands with a double well structure in lower branch. This novel dispersion behaviour greatly enriches the ground-state phase diagram [10][11][12][13][14][15][16][17] and the collective excitation dynamics [18][19][20][21], compared with the parabolic dispersion of ordinary atomic BECs. By control over experimental parameters, dynamics involving two spin-orbit-coupled bands can be excited and it has been shown experimentally that a quantum quench can result in intriguing Zitterbewegung oscillations [22].…”

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confidence: 99%

“…(3) The one dimensional spin-orbit coupling is generated experimentally by applying two Raman beams that couple two pseudo-spin states [1,9,17,18,[20][21][22][23]26]. γ characterizes the spin-orbit coupling strength k Ram /m with k Ram being wave number of Raman beams, δ is the detuning, and Ω is the Rabi frequency.…”

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confidence: 99%

Nonlinear dynamics of a spin-orbit-coupled Bose-Einstein condensate

2019

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Single-particle dynamics of a spin-orbit-coupled Bose-Einstein condensate has recently been investigated in experiments that explore the physics of Landau-Zener tunneling and of the Zitterbewegung. In this paper, we study the influence of a nonlinearity due to interactions on these dynamics and show that the dispersion relation develops interesting loop structures. The atoms can move along the nonlinear dispersion curve in the presence of a weak acceleration force and we show that the loops lead to straightforward nonlinear Landau-Zener tunneling. However, we find that for the Zitterbewegung, induced by a sudden quench in the spin-orbit coupling parameters, the nonlinear dispersion is irrelevant.

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Collective dipole oscillations of a spin-orbit coupled Fermi gas

Cited by 8 publications

References 35 publications

Large-momentum tail of one-dimensional Fermi gases with spin-orbit coupling

Large-momentum tail of one-dimensional Fermi gases with spin-orbit coupling

Collective oscillation modes of a superfluid Bose–Fermi mixture

Nonlinear dynamics of a spin-orbit-coupled Bose-Einstein condensate

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