Abstract: Diagrammatic interpretation of bad-metallic transport in the 2D Hubbard model
Strange metallicity in correlated charge transport, particularly emerging in the course of the evolution from a conventional metal toward an antiferromagnetic insulator, is one of the long-standing and still actively pursued problems in modern condensed matter physics. Using diagrammatic Monte Carlo, we present controlled transport results in the correlated regime of the prototypical two-dimensional Hubbard model, and further elucidate their underlying structure via various decompositions. These include the Nernst–Einstein decomposition, spin-resolved diagrammatic vertex decomposition, and peak and spatial decompositions of the optical spectrum. As a result, we observe a robust temperature scaling of the diffusion constant and identify the special role of opposite-spin vertex diagrams at half filling. In the optimally doped regime, we clearly observe the coexistence of a central Drude peak and high-energy excitations, and discuss their spatial decomposition, which is challenging to access experimentally.