Dipole Oscillation in a Bose–Fermi Superfluid Mixture of ^(41)K and ~6Li

We study the relation between the bosonic frequency shift of a dipole oscillation and the fermionic compressibility in a Bose-Fermi super fluid mixture. Our results show that the A transition occurs in such a system, which interprets the perplexing phenomenon observed in the recent experiment [arXiv：1705.04496]. In that experiment,the frequency shift of the bosonic gas was measured with different fermion-fermion s-wave scattering lengths af. The most striking feature of their measurement is that the frequency shift shows a puzzling non-monotonic behavior around 1/kFaf（？）-0.2 with kF being the Fermi momentum. In the present work, the relation between the bosonic frequency shift and the compressibility of the Fermi gas is revealed by means of the equation of state of the super fluid mixture. Making use of the relation, we find that the compressibility of Fermi gas shows a ∧-like shape around 1/kFaf（？）-0.2. We would like to stress that no free parameter is used in our calculation and our results can be further testified in a future experiment.

Tunneling dynamics of superfluid Fermi gas in a triple-well potential

The tunneling dynamics of superfluid Fermi gas in a triple-well potential in the unitarity regime is investigated in the present paper. The fixed points of the （0,0） mode and the （π, π） mode are given. We find that the interaction parameter U and the coupling strength k could have an extreme effect on the quantum tunneling dynamics. We also find that, in the zero mode, only Josophson oscillation appears. However, for the mode, the trapping phenomena take place. An irregular oscillation of the particle number in each well could appear by adjusting the scanning period T. It is noted that if the scanning period is less than a critical point T＊, the particle number will come back to the fixed point with small oscillation, while if T 〉 T＊ the particle number cannot come back to the fixed point, but with irregular oscillations. The dependence of the critical point T＊ on the system parameter of coupling strength k is numerically given.

Dark lump excitations in superfluid Fermi gases

We study the linear and nonlinear properties of two-dimensional matter-wave pulses in disk-shaped superfluid Fermi gases. A Kadomtsev-Petviashvili I （KPI） solitary wave has been realized for superfluid Fermi gases in the limited cases of Bardeen-Coope-Schrieffer （BCS） regime, Bose-Einstein condensate （BEC） reginle, and unitarity regime. One- lump solution as well as one-line soliton solutions for the KPI equation are obtained, and two-line soliton solutions with the same amplitude are also studied in the limited cases. The dependence of the lump propagating velocity and the sound speed of two-dimensional superfluid Fermi gases on the interaction parameter are investigated for the limited cases of BEC and unitarity.

Superfluid Fermi Gases in a Rotating Anharmonic Trap

The quadrupole mode frequency, the monopole mode frequency, and the critical rotational frequency for stirring a single vortex nucleation along the BEC-BCS crossover are obtained. The results show that, in a rotating anisotropic anharmonic trap, the quadrupole mode frequency and the critical rotational frequency for stirring a single vortex nucleation are modified significantly when the system crosses from the BEC side to the BCS side： the anisotropy of the trap induces a downshiff of the quadrupole mode frequency and the critical rotational frequency and helps the vortex formation in the system, while an anharmonic trap induces an upshift of the quadrupole mode frequency and the critical rotational frequency and suppresses the vortex formation in the system.

Landau damping in a dipolar Bose–Fermi mixture in the Bose–Einstein condensation(BEC) limit

By using a mean-field approximation which describes the coupled oscillations of condensate and noncondensate atoms in the collisionless regime, Landau damping in a dilute dipolar Bose-Fermi mixture in the BEC limit where Fermi superfluid is treated as tightly bounded molecules, is investigated. In the case of a uniform quasi-two-dimensional （2D） case, the results for the Landau damping due to the Bose-Fermi interaction are obtained at low and high temperatures. It is shown that at low temperatures, the Landau damping rate is exponentially suppressed. By increasing the strength of dipolar interaction, and the energy of boson quasiparticles, Landau damping is suppressed over a broader temperature range.

Probing two Higgs oscillations in a one-dimensional Fermi superfluid with Raman-type spin-orbit coupling

We theoretically investigate the Higgs oscillation in a one-dimensional Raman-type spin–orbit-coupled Fermi superfluid with the time-dependent Bogoliubov–de Gennes equations.By linearly ramping or abruptly changing the effective Zeeman field in both the Bardeen–Cooper–Schrieffer state and the topological superfluid state,we find the amplitude of the order parameter exhibits an oscillating behaviour over time with two different frequencies(i.e.,two Higgs oscillations)in contrast to the single one in a conventional Fermi superfluid.The observed period of oscillations has a great agreement with the one calculated using the previous prediction[Volkov and Kogan,J.Exp.Theor.Phys.38,1018(1974)],where the oscillating periods are now determined by the minimums of two quasi-particle spectrum in this system.We further verify the existence of two Higgs oscillations using a periodic ramp strategy with theoretically calculated driving frequency.Our predictions would be useful for further theoretical and experimental studies of these Higgs oscillations in spin–orbit-coupled systems.

Self-trapping and Macroscopic Tunnelling of Superfluid Fermi Gases in Multi-well Potentials

We study the tunnelling dynamics of superfluid Fermi gases trapped in multi-well system along the BEC-BCS crossover. Within the hydrodynamical model and by using the multi-mode approximation, the self-trapping dynamics of superfluid Fermi gases in multi-well system are obtained numerically. We find that the self-trapping to diffusion transition strongly depends on the well number. When the well number is less than three, the self-trapped state takes place easier on the BEC side than that on the BCS side. However, when the well number is larger than three, the self-trapped state takes place easier on the BCS side instead of the BEC side. Furthermore, by considering a superfluid of 40K atoms, we obtain the zero-mode and π-mode Josephson frequencies of coherent atomic oscillations in double-well system. It is noteworthy that the Josephson mode, especially, the existence of π-mode frequency strongly depends on the atoms number on the BCS side.

Diffusive Thermal Conductivity of Superfluid Fermi Gas in p-Wave State at Low Temperatures

The diffusive thermal conductivity tensor of p-wave superfluid at low temperatures is calculated by using the Boltzmann equation approach. We use the Sykes and Brooker procedure and show that Kxx is equal to Kyy and these are related to T-1, also Kxx is proporated to T-3.