Bad metallic transport in a cold atom Fermi-Hubbard system.

Brown, Peter T; Mitra, Debayan; Guardado-Sanchez, Elmer; Nourafkan, Reza; Reymbaut, Alexis; Hébert, Charles-David; Bergeron, Simon; Tremblay, A-M S et al. · Science · 2019

basic_science · Level V

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Abstract

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 lithium-6 in a two-dimensional 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 by 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 developed in this study may be applied to measurements of other transport quantities, including the optical conductivity and thermopower.