Strong interactions in many-body quantum systems complicate the interpretation of charge transport in such materials. To shed light on this problem, we study transport in a clean quantum system: ultracold 6 Li in a 2D optical lattice, a testing ground for strong interaction physics in the Fermi-Hubbard model. We determine the diffusion constant by measuring the relaxation of an imposed density modulation and modeling its decay hydrodynamically. The diffusion constant is converted to a resistivity using the Nernst-Einstein relation. That resistivity exhibits a linear temperature dependence and shows no evidence of saturation, two characteristic signatures of a bad metal. The techniques we develop here may be applied to measurements of other transport quantities, including the optical conductivity and thermopower. arXiv:1802.09456v2 [cond-mat.quant-gas]

l 1−Im[Σ(iω 0 )] ll /ω 0 with ω 0 the first Matsubara frequency, is related to the effective mass enhancement via m * l /m LDA l = Z −1 l . We find Z −1 l ∼ 5.3, 3.8, 3.8 for arXiv:1808.02527v1 [cond-mat.supr-con]