Dynamically enhanced magnetic incommensurability: Effects of local dynamics on nonlocal spin correlations in a strongly correlated metal

We compute the spin susceptibility of the two-dimensional Hubbard model away from half-filling, and analyze the impact of frequency-dependent vertex corrections as obtained from the dynamical mean field theory (DMFT). We find that the local dynamics captured by the DMFT vertex strongly affects nonlocal spin correlations, and thus the momentum dependence of the spin susceptibility. While the widely used random-phase approximation yields commensurate N\'eel-type antiferromagnetism as the dominant instability over a wide doping range, the vertex corrections favor incommensurate ordering wave vectors away from $(\ensuremath{\pi},\ensuremath{\pi})$. Our results indicate that the connection between the magnetic ordering wave vector and the Fermi surface geometry, familiar for weakly interacting systems, can hold in a strongly correlated metal, too.