Transport in the 2D Fermi-Hubbard model: Lessons from weak coupling

Recent cold atom experiments have observed bad and strange metal behaviors in strongly-interacting Fermi-Hubbard systems. Motivated by these results, we calculate the thermoelectric transport properties of a 2D Fermi-Hubbard system in the weak coupling limit using quantum kinetic theory. We find that many features attributed to strong correlations are also found at weak coupling. In particular, for temperatures T>t the electrical resistivity is nearly linear in temperature despite the fact that the quasiparticle scattering rate is non-linear and changes by nearly an order of magnitude. We argue that this asymptotic behavior is a general feature of systems with a finite spectral width, which implies that there is no MIR bound on the resistivity in single-band models. Due to nesting, the T-linear resistivity persists down to T=0 at half filling. Our work sheds light on the transport regimes accessible in ultracold atom experiments, which can differ substantially from those in condensed matter systems. Disentangling these band-structure effects from the physics of strong correlations is a major challenge for future experiments.