Transverse spin diffusion in strongly interacting Fermi gases

TL;DR

This paper calculates spin diffusion in strongly interacting Fermi gases across various conditions, revealing polarization-dependent behaviors and minimum diffusivities near quantum limits, with results aligning with recent experiments.

Contribution

It provides a comprehensive kinetic theory analysis of spin diffusion in Fermi gases at arbitrary temperature, polarization, and interaction strength, including new insights into transverse diffusivity behavior.

Findings

Transverse spin diffusivity D_⊥ approaches a finite value as T→0 in Fermi liquids.

Diffusivities reach a minimum near the quantum limit in 3D unitary gases.

In 2D, D_⊥ attains a minimum at strong coupling and matches experimental data.

Abstract

We compute spin diffusion in a dilute Fermi gas at arbitrary temperature, polarization and strong interaction in the normal phase using kinetic theory. While the longitudinal spin diffusivity depends weakly on polarization and diverges for small temperatures, the transverse spin diffusivity D_\perp has a strong polarization dependence and approaches a finite value for T->0 in the Fermi liquid phase. For a 3D unitary Fermi gas at infinite scattering length the diffusivities reach a minimum near the quantum limit of diffusion \hbar/m in the quantum degenerate regime and are strongly suppressed by medium scattering, and we discuss the importance of the spin-rotation effect. In two dimensions, D_\perp attains a minimum at strong coupling -1 < ln(kFa2D) < 1 and reaches D_\perp~0.2...0.3\hbar/m at large polarization. These values are consistent with recent measurements of two-dimensional ultracold atomic gases in the strong coupling regime.