Fermi gas experiments

In this work we establish constraints on the temperature dependence of the shear viscosity $\ensuremath{\eta}$ in the superfluid phase of a dilute Fermi gas in the unitary limit. Our results are based on analyzing experiments that measure the aspect ratio of a deformed cloud after release from an optical trap. We discuss how to apply the two-fluid formalism to the unitary gas and provide a suitable parametrization of the equation of state. We show that in expansion experiments the difference between the normal and superfluid velocities remains small and can be treated as a perturbation. We find that expansion experiments favor a shear viscosity that decreases significantly in the superfluid regime. Using an exponential parametrization, we find $\ensuremath{\eta}({T}_{c}/2{T}_{F})\ensuremath{\lesssim}0.37[\ensuremath{\eta}({T}_{c}/{T}_{F})]$, where ${T}_{c}$ is the critical temperature and ${T}_{F}$ is the local Fermi temperature of the gas.In this work we establish constraints on the temperature dependence of the shear viscosity $\ensuremath{\eta}$ in the superfluid phase of a dilute Fermi gas in the unitary limit. Our results are based on analyzing experiments that measure the aspect ratio of a deformed cloud after release from an optical trap. We discuss how to apply the two-fluid formalism to the unitary gas and provide a suitable parametrization of the equation of state. We show that in expansion experiments the difference between the normal and superfluid velocities remains small and can be treated as a perturbation. We find that expansion experiments favor a shear viscosity that decreases significantly in the superfluid regime. Using an exponential parametrization, we find $\ensuremath{\eta}({T}_{c}/2{T}_{F})\ensuremath{\lesssim}0.37[\ensuremath{\eta}({T}_{c}/{T}_{F})]$, where ${T}_{c}$ is the critical temperature and ${T}_{F}$ is the local Fermi temperature of the gas.

arXiv:2105.05284Physical Review AAug 13, 20212 citations

Probing ultracold Fermi atoms with a single ion

Yu. B. Sherkunov, B. A. Muzykantskiǐ, N. d’Ambrumenil +1 more

We show that the recently proposed ionic microscope setup [Kollath et al., Phys. Rev. A 76, 063602 (2007)] could be adapted to measure the local single-particle energy distribution of a degenerate Fermi gas in situ with the resolution on the nanometer scale. We study an ion held in a Paul trap in an atomic Fermi gas and compute the two-photon Raman photo-association rate of the ion and an atom. We show that, as a function of the detunings between the frequencies of the two incident lasers and energies in the atom-ion system, the photoassociation rate directly measures the single-particle energy distribution in the Fermi gas around the ion. We describe an experiment to measure the photoassociation rate of a trapped ion and argue that, as the position of the ion can be scanned through the Fermi gas, this experiment directly probes the local energy and spin-state distribution of the Fermi gas.We show that the recently proposed ionic microscope setup [Kollath et al., Phys. Rev. A 76, 063602 (2007)] could be adapted to measure the local single-particle energy distribution of a degenerate Fermi gas in situ with the resolution on the nanometer scale. We study an ion held in a Paul trap in an atomic Fermi gas and compute the two-photon Raman photo-association rate of the ion and an atom. We show that, as a function of the detunings between the frequencies of the two incident lasers and energies in the atom-ion system, the photoassociation rate directly measures the single-particle energy distribution in the Fermi gas around the ion. We describe an experiment to measure the photoassociation rate of a trapped ion and argue that, as the position of the ion can be scanned through the Fermi gas, this experiment directly probes the local energy and spin-state distribution of the Fermi gas.

arXiv:0802.3158Physical Review AFeb 4, 200924 citations

Fermi Gases

WORLD SCIENTIFIC eBooksOct 1, 20080 citations

Fermi gas

K. Yamada

Cambridge University Press eBooksSep 23, 20040 citations

Dipole Oscillation in a Bose–Fermi Superfluid Mixture of 41 K and 6 Li

Ren Zhang

We study the relation between the bosonic frequency shift of a dipole oscillation and the fermionic compressibility in a Bose–Fermi superfluid mixture. Our results show that the Λ 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 a f . The most striking feature of their measurement is that the frequency shift shows a puzzling non-monotonic behavior around 1/ k F a f ≃ −0.2 with k F 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 superfluid mixture. Making use of the relation, we find that the compressibility of Fermi gas shows a Λ-like shape around 1/ k F a f ≃ −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.We study the relation between the bosonic frequency shift of a dipole oscillation and the fermionic compressibility in a Bose–Fermi superfluid mixture. Our results show that the Λ 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 a f . The most striking feature of their measurement is that the frequency shift shows a puzzling non-monotonic behavior around 1/ k F a f ≃ −0.2 with k F 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 superfluid mixture. Making use of the relation, we find that the compressibility of Fermi gas shows a Λ-like shape around 1/ k F a f ≃ −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.

Chinese Physics LettersApr 1, 20182 citations

{T}_{c}

is the critical temperature and

{T}_{F}

is the local Fermi temperature of the gas.