Critical strange metal from fluctuating gauge fields in a solvable random model*

Building upon techniques employed in the construction of the Sachdev-Ye-Kitaev model, which is a solvable (0+ 1)-dimensional model of a non-Fermi liquid, we develop a solvable infinite-ranged random-hopping model of fermions coupled to fluctuating U (1) gauge fields. In a specific large-N limit, our model realizes a gapless non-Fermi-liquid phase, which combines the effects of hopping and interaction terms. We derive the thermodynamic properties of the non-Fermi-liquid phase realized by this model and the charge transport properties of an infinite-dimensional version with spatial structure. We also describe a Higgs transition from this non-Fermi-liquid "strange metal" phase to a weakly-interacting "pseudogap" phase with a relatively reduced low-energy fermion density of states, and gapped gauge field fluctuations.