Abstract

Understanding transport in strongly interacting systems of fermions is one of the outstanding challenges in many-body physics. There exist many open questions even on the qualitative features of such transport, whether it can be described by quasi-particles, whether heat, charge and spin are transported together or separately, and how transport properties change across phase transitions. I will present measurements of sound attenuation in strongly interacting, homogeneous Fermi gases, which reveal quantum limited sound diffusivity even in the superfluid regime. For Fermi gases in the Hubbard regime, observed under a microscope with single-atom resolution, we performed studies of spin transport in the Mott insulating regime, where charge is frozen but spins are free to diffuse. We obtain spin diffusivities revealing super-exchange scaling, with contributions from direct tunnelling of spins facilitated by doublon-hole fluctuations.