Metal to insulator crossover and non-Fermi-liquid physics in the half-filled 2d Hubbard model

We present a controlled study of the finite-temperature crossover from the metallic to insulating regime in the half-filled 2D Hubbard model using Diagrammatic Monte Carlo techniques in the thermodynamic limit. Our results for one- and two-body properties confirm absence of the metal- to-insulator transition at any non-zero coupling and relate the insulating behavior to development of extended antiferromagnetic (AFM) correlations. The crossover is marked by the AFM correlation length extending beyond one lattice constant and involves an intermediate non-Fermi-liquid regime with a partially gapped Fermi surface. We observe the peculiar behavior of thermodynamic observables at the crossover indicative of the Slater-type insulator scenario.