Spin Drag in Ultracold Fermi Mixtures with Repulsive Interactions

http://arxiv.org/PS_cache/arxiv/pdf/1012/1012.3827v1.pdfWe calculate the spin-drag relaxation rate for a two-component ultracold atomic Fermi gas with positive scattering length between the two spin components. In one dimension we find that it vanishes linearly with temperature. In three dimensions the spin-drag relaxation rate vanishes quadratically with temperature for sufficiently weak interactions. This quadratic temperature dependence is present, up to logarithmic corrections, in the two- dimensional case as well. For stronger interaction the system exhibits a Stoner ferromagnetic phase transition in two and three dimensions. We show that the spin-drag relaxation rate is enhanced by spin fluctuations as the temperature approaches the critical temperature of this transition from above.This work was supported by the Stichting voor Fundamenteel Onderzoek der Materie (FOM), the Netherlands Organization for Scienti c Research (NWO), and by the European Research Council (ERC). G.V. acknowledges support from NSF Grant No. 0705460