Low-momentum dynamic structure factor of a strongly interacting Fermi gas at finite temperature: A two-fluid hydrodynamic description

Abstract

We provide a description of the dynamic structure factor of a homogeneous unitary Fermi gas at low momentum and low frequency, based on the dissipative two-fluid hydrodynamic theory. The viscous relaxation time is estimated and is used to determine the regime where the hydrodynamic theory is applicable and to understand the nature of sound waves in the density response near the superfluid phase transition. By collecting the best knowledge on the shear viscosity and thermal conductivity known so far, we calculate the various diffusion coefficients and obtain the damping width of the (first and second) sounds. We find that the damping width of the first sound is greatly enhanced across the superfluid transition and very close to the transition the second sound might be resolved in the density response for the transferred momentum up to the half of Fermi momentum. Our work is motivated by the recent measurement of the local dynamic structure factor at low momentum at Swinburne University of Technology and the on-going experiment on sound attenuation of a homogeneous unitary Fermi gas at Massachusetts Institute of Technology. We discuss how the measurement of the velocity and damping width of the sound modes in low-momentum dynamic structure factor may lead to an improved determination of the universal superfluid density, shear viscosity and thermal conductivity of a unitary Fermi gas.

13 pages, 12 figures

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Cited by in corpus (13)

• Observation of first and second sound in a BKT superfluid
• Universal Sound Diffusion in a Strongly Interacting Fermi Gas
• Measuring the Hydrodynamic Linear Response of a Unitary Fermi Gas
• High Frequency Sound in a Unitary Fermi Gas
• Phononic collective excitations in superfluid Fermi gases at nonzero temperatures
• Quantum critical thermal transport in the unitary Fermi gas
• Dynamical structure factors of a two-dimensional Fermi superfluid within random phase approximation
• Hydrodynamic Relaxation in a Strongly Interacting Fermi Gas
• Second sound with ultracold atoms: A brief historical account
• Dynamic structure factors of a strongly interacting Fermi superfluid near an orbital Feshbach resonance across the phase transition from BCS to Sarma superfluid
• Energy absorption spectroscopy of unitary Fermi gases in a uniform potential
• Universal Density Shift Coefficients for the Thermal Conductivity and Shear Viscosity of a Unitary Fermi Gas
• Dynamical structure factor and a new method to measure the pairing gap in two-dimensional attractive Fermi-Hubbard model