Abstract We revisit the properties of the two-component Fermi gas with short-range interactions in three dimensions, in the limit where the s -wave scattering length diverges. Such a unitary Fermi gas possesses universal thermodynamic and dynamical observables that are independent of any interaction length scale. Focusing on trapped systems of N fermions, where N ≤ 10 , we investigate how well we can determine the zero-temperature behavior of the many-body system from published few-body data on the ground-state energy and the contact. For the unpolarized case, we find that the Bertsch parameters extracted from trapped few-body systems all lie within 15% of the established value. Furthermore, the few-body values for the contact are well within the range of values determined in the literature for the many-body system. In the limit of large spin polarization, we obtain a similar accuracy for the polaron energy, and we estimate the polaron’s effective mass from the dependence of its energy on N . We also compute an upper bound for the squared wave-function overlap between the unitary Fermi system and the non-interacting ground state, both for the trapped and uniform cases. This allows us to prove that the trapped unpolarized ground state at unitarity has zero overlap with its non-interacting counterpart in the many-body limit N → ∞ .Abstract We revisit the properties of the two-component Fermi gas with short-range interactions in three dimensions, in the limit where the s -wave scattering length diverges. Such a unitary Fermi gas possesses universal thermodynamic and dynamical observables that are independent of any interaction length scale. Focusing on trapped systems of N fermions, where N ≤ 10 , we investigate how well we can determine the zero-temperature behavior of the many-body system from published few-body data on the ground-state energy and the contact. For the unpolarized case, we find that the Bertsch parameters extracted from trapped few-body systems all lie within 15% of the established value. Furthermore, the few-body values for the contact are well within the range of values determined in the literature for the many-body system. In the limit of large spin polarization, we obtain a similar accuracy for the polaron energy, and we estimate the polaron’s effective mass from the dependence of its energy on N . We also compute an upper bound for the squared wave-function overlap between the unitary Fermi system and the non-interacting ground state, both for the trapped and uniform cases. This allows us to prove that the trapped unpolarized ground state at unitarity has zero overlap with its non-interacting counterpart in the many-body limit N → ∞ .

arXiv:1612.02131Journal of Physics B Atomic Molecular and Optical PhysicsJan 18, 201731 citations

Unitarity-limited behavior of three-body collisions in a p -wave interacting Fermi gas

Muhammad Waseem, Jun Yoshida, Taketo Saito +1 more

We experimentally investigate the unitarity-limited behavior of the three-body loss near a $p$ -wave Feshbach resonance in a single-component Fermi gas of $^{6}\mathrm{Li}$ atoms. At the unitarity limit, the three-body loss coefficient ${L}_{3}$ exhibits universality in the sense that it is independent of the interaction strength and follows the predicted temperature scaling law of ${L}_{3}\ensuremath{\propto}{T}^{\ensuremath{-}2}$. When decreasing the interaction strength from the unitarity regime, the three-body loss coefficient as a function of the interaction strength and temperature can be described by the theory based on the association of an excited resonant quasibound state and its relaxation into a deep stable dimer by collision with a third atom in the framework of the standard Breit-Wigner theoretical approach. The results reported here are important to understand the properties of a resonant $p$ -wave Fermi gas in the prospect of quantum few- and many-body physics.We experimentally investigate the unitarity-limited behavior of the three-body loss near a $p$-wave Feshbach resonance in a single-component Fermi gas of $^{6}\mathrm{Li}$ atoms. At the unitarity limit, the three-body loss coefficient ${L}_{3}$ exhibits universality in the sense that it is independent of the interaction strength and follows the predicted temperature scaling law of ${L}_{3}\ensuremath{\propto}{T}^{\ensuremath{-}2}$. When decreasing the interaction strength from the unitarity regime, the three-body loss coefficient as a function of the interaction strength and temperature can be described by the theory based on the association of an excited resonant quasibound state and its relaxation into a deep stable dimer by collision with a third atom in the framework of the standard Breit-Wigner theoretical approach. The results reported here are important to understand the properties of a resonant $p$-wave Fermi gas in the prospect of quantum few- and many-body physics.

arXiv:1803.07530Physical Review AAug 8, 201832 citations

Thermodynamics of Trapped Imbalanced Fermi Gases at Unitarity

J. M. Diederix, Henk T. C. Stoof

arXiv:1102.3320Lecture notes in physicsOct 19, 20115 citations

Variational theory of two-fluid hydrodynamic modes at unitarity

Edward Taylor, Hui Hu, Xia-Ji Liu +1 more

We present the results of a variational calculation of the frequencies of the low-lying Landau two-fluid hydrodynamic modes in a trapped Fermi superfluid gas at unitarity. Landau's two-fluid hydrodynamics is expected to be the correct theory of Fermi superfluids at finite temperatures close to unitarity, where strong interactions give rise to collisional hydrodynamics. Two-fluid hydrodynamics predicts the existence of in-phase modes in which the superfluid and normal fluid components oscillate together, as well as out-of-phase modes where the two components move against each other. We prove that, at unitarity, the dipole and breathing in-phase modes are locally isentropic. Their frequencies are independent of temperature and are the same above and below the superfluid transition, a feature due as much to the harmonic trapping potential as to the thermodynamic properties at unitarity. The out-of-phase modes, in contrast, are strongly dependent on temperature and hence can be used to test the thermodynamic properties and superfluid density of a Fermi gas at unitarity. We give numerical results for the frequencies of these modes as function of temperature in an isotropic trap at unitarity.We present the results of a variational calculation of the frequencies of the low-lying Landau two-fluid hydrodynamic modes in a trapped Fermi superfluid gas at unitarity. Landau's two-fluid hydrodynamics is expected to be the correct theory of Fermi superfluids at finite temperatures close to unitarity, where strong interactions give rise to collisional hydrodynamics. Two-fluid hydrodynamics predicts the existence of in-phase modes in which the superfluid and normal fluid components oscillate together, as well as out-of-phase modes where the two components move against each other. We prove that, at unitarity, the dipole and breathing in-phase modes are locally isentropic. Their frequencies are independent of temperature and are the same above and below the superfluid transition, a feature due as much to the harmonic trapping potential as to the thermodynamic properties at unitarity. The out-of-phase modes, in contrast, are strongly dependent on temperature and hence can be used to test the thermodynamic properties and superfluid density of a Fermi gas at unitarity. We give numerical results for the frequencies of these modes as function of temperature in an isotropic trap at unitarity.

arXiv:0711.0561Physical Review AMar 7, 200829 citations

We experimentally investigate the unitarity-limited behavior of the three-body loss near a

p

-wave Feshbach resonance in a single-component Fermi gas of

^{6}\mathrm{Li}

atoms. At the unitarity limit, the three-body loss coefficient

{L}_{3}

exhibits universality in the sense that it is independent of the interaction strength and follows the predicted temperature scaling law of ${L}_{3}\ensuremath{\propto}{T}^{\ensuremath{-}2}$. When decreasing the interaction strength from the unitarity regime, the three-body loss coefficient as a function of the interaction strength and temperature can be described by the theory based on the association of an excited resonant quasibound state and its relaxation into a deep stable dimer by collision with a third atom in the framework of the standard Breit-Wigner theoretical approach. The results reported here are important to understand the properties of a resonant

p

-wave Fermi gas in the prospect of quantum few- and many-body physics.