Abstract
We examine spin diffusion in a two-component homogeneous Fermi gas in the normal phase. Using a variational approach, analytical results are presented for the spin diffusion coefficient and the related spin relaxation time as a function of temperature and interaction strength. For low temperatures, strong correlation effects are included through the Landau parameters, which we extract from Monte Carlo results. We show that the spin diffusion coefficient has a minimum for a temperature somewhat below the Fermi temperature with a value that approaches the quantum limit ∼ℏ/m in the unitarity regime, where m is the particle mass. Finally, we derive a value for the low-temperature shear viscosity in the normal phase from the Landau parameters.
Highlights
Cold atomic gases provide a unique possibility to study many-body physics in a controlled way as one can tune properties such as the strength and sign of the interaction as well as the population in various internal states
The strong coupling effects are contained in the Landau parameters which are extracted from Monte Carlo calculations
Combined with the relevant Landau parameters extracted from non-perturbative Monte-Carlo calculations, we can in this way derive reliable results for D in the strongly interacting normal phase [26, 27]
Summary
Cold atomic gases provide a unique possibility to study many-body physics in a controlled way as one can tune properties such as the strength and sign of the interaction as well as the population in various internal states. Using methods from from string theory, it has been shown that the viscosity of a class of strongly interacting many-body systems obey the bound η/s > /4πkB where s is the entropy density [21], and it has been conjectured that this bound holds for all fluids [22] This has made the study of the viscosity of cold atomic Fermi gases in the unitarity limit directly relevant to other fields including quark-gluon and high energy physics [23]. The strong coupling effects are contained in the Landau parameters which are extracted from Monte Carlo calculations In this way, we expect to obtain reliable results for D even in the unitarity limit. We calculate the closely related spin relaxation time, and briefly discuss how η can be extracted from the Landau parameters
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