title: Quantum mechanical limitations to spin diffusion in the unitary Fermi gas.
abstract: We compute spin transport in the unitary Fermi gas using the strong-coupling Luttinger-Ward theory. In the quantum degenerate regime the spin diffusivity attains a minimum value of D(s) Symbol: see text] 1.3 ħ/m approaching the quantum limit of diffusion for a particle of mass m. Conversely, the spin drag rate reaches a maximum value of Γ(sd) [Symbol: see text] 1.2k(B)T(F)/ħ in terms of the Fermi temperature T(F). The frequency-dependent spin conductivity σ(s)(ω) exhibits a broad Drude peak, with spectral weight transferred to a universal high-frequency tail σ(s) (ω → ∞) = ħ(1/2)C/3π(mω)(3/2) proportional to the Tan contact density C. For the spin susceptibility χ(s)(T) we find no downturn in the normal phase.
authors.affiliation: Physik Department, Technische Universität München, D-85747 Garching, Germany.
authors.forename: Tilman
authors.initials: T
authors.lastname: Enss
authors.forename: Rudolf
authors.initials: R
authors.lastname: Haussmann