A New View of the Mott-Hubbard Transition: Renormalization of the Fermi-Surface Topology

We present the renormalization of the (underlying) Fermi-surface topology in the Hubbard model on a square lattice with frustrating hopping, that is relevant for the physics of high-temperature superconductors. With the help of novel high precision variational tools, including Jastrow factors and backflow correlations, we show that the Fermi surface renormalizes to perfect nesting at the interaction-driven Mott-Hubbard transition and in the large interaction limit. Moreover, we present new results for the density-driven Mott-Hubbard transition, investigating the Fermi-surface renormalization flow as a function of doping, where the renormalization occurs only when the half-filled case is insulating. We associate the flow to the appearance of a van Hove singularity at the Fermi level at small doping, that is interpreted as an instability to magnetic order. Finally, we show also that Fermi surface renormalization is associated to a strong crossover at finite doping for the critical $U$ corresponding to the Mott-Hubbard transition.