Energy-absorption spectroscopy of unitary Fermi gases in a uniform potential

We propose to use the energy absorption spectroscopy to measure the kinetic coefficients of unitary Fermi gases in a uniform potential. We show that, in our scheme, the energy absorption spectrum is proportional to the dynamic structure factor of the system. The profile of the spectrum depends on the shear viscosity $\eta$, the thermal conductivity $\kappa$, and the superfluid bulk viscosity ${\xi }_3$. We show that extraction of these coefficients from the spectrum is achievable in present experiments.

Figure 1

The energy absorption spectrum $\mathrm{\Gamma }(\mathbf{q},\omega )$ of unitary Fermi gases with $\left|\mathbf{q}\right|/k_F=0.1$ in the superfluid phase for $T=0.11T_F$ and $T=0.12T_F$. The approximation ${\mathrm{\Gamma }}_{\mathrm{app}}(\mathbf{q},\omega )$ is plotted for comparison. The inset shows the full profiles of the first sound peaks.

Figure 2

The energy absorption spectrum $\mathrm{\Gamma }(\mathbf{q},\omega )$ of unitary Fermi gases with $\left|\mathbf{q}\right|/k_F=0.1$ in the normal phase for $T=0.4T_F$ and $T=T_F$. The approximation ${\mathrm{\Gamma }}_{\mathrm{app}}(\mathbf{q},\omega )$ is plotted for comparison. The inset plots $\mathrm{\Gamma }(\mathbf{q},\omega )/{\omega }^2$, which shows the Rayleigh peak at zero frequency.

Figure 3

Relative errors of extracted kinetic coefficients versus noise magnitude $\mathrm{\Delta }$ in units of percentage. (a) The case of $T=0.12T_F$. (b) The case of $T=0.4T_F$.