Interconnected Renormalization of Hubbard Bands and Green's Function Zeros in Mott Insulators Induced by Strong Magnetic Fluctuations

We analyze the role of spatial electronic correlations and, in particular, of the magnetic fluctuations in Mott insulators. A half-filled Hubbard model is solved at large strength of the repulsion U on a two-dimensional square lattice using an advanced diagrammatic non-perturbative approach capable of going beyond Hartree-Fock and single-site dynamical mean-field theories. We show that at high temperatures the magnetic fluctuations are weak, and the electronic self-energy of the system is mainly local and is well reproduced by the atomic (Hubbard-I) approximation. Lowering the temperature toward the low-temperature magnetically ordered phase, the non-locality of the self-energy becomes crucial in determining the dispersion of the Hubbard bands and of the Green's function zeros. We therefore establish a precise link between the Luttinger surface and the momentum-structure of the Hubbard bands.