Transport measurement is one of the most important ways to study the properties of matter. In this article, we discuss recent experiments in ultracold atomic gases where the analog of Landauer transport in mesoscopic devices is realized and spin dynamics in a strongly interacting Fermi gas is probed. In the latter case, we pay special attention to the peculiarity of spin dynamics due to identical spin rotation effect which leads to a novel form of spin diffusion current. This modifies the usual diffusion equation into a more complicated form and leads to important consequence for, in particular, transverse spin diffusion in ultracold Fermi gases.
In this Rapid Communication we investigate the fluctuation effects on the transport properties of unitary Fermi gases in the vicinity of the superfluid transition temperature
Tc. Based on the time-dependent Ginzburg-Landau formalism of the Bose-Einstein condensate--BCS crossover, we investigate both the residual resistivity below
Tc induced by phase slips and the paraconductivity above
Tc due to pair fluctuations. These two effects have been well studied in the weak-coupling BCS superconductor and here we generalize them to the unitary regime of ultracold Fermi gases. We find that while the residual resistivity below
Tc increases as one approaches the unitary limit, consistent with recent experiments, the paraconductivity exhibits nonmonotonic behavior. Our results can be verified with the recently developed transport apparatus using mesoscopic channels.