We show that the numerically exact bold-line diagrammatic theory for the 2d Hubbard model exhibits a non-Fermi-liquid (NFL) strange metal state, which is connected to the SYK NFL in the strong-interaction limit. The solution for the doped system features the expected phenomenology with the NFL near half-filling at strong couplings and in a wide temperature range enclosed by the atomic state at high temperatures and a Fermi liquid at low temperatures. We demonstrate, however, that this behavior in the weakly doped regime is due to the unphysical branch of the Luttinger-Ward functional. On the other hand, our analysis shows that the NFL physics is realized at larger doping.
@article{arxiv.2012.06159,
title = {Strange Metal Solution in the Diagrammatic Theory for the $2d$ Hubbard Model},
author = {Aaram J. Kim and Philipp Werner and Evgeny Kozik},
journal= {arXiv preprint arXiv:2012.06159},
year = {2020}
}