Lifshitz transition driven by spin fluctuations and spin-orbit renormalization in NaOsO3

In systems where electrons form both dispersive bands and small local spins, we show that changes in the spin configuration can tune the bands through a Lifshitz transition, resulting in a continuous metal-insulator transition associated with a progressive change in the Fermi surface topology. In contrast to the Mott-Hubbard and Slater pictures, this spin-driven Lifshitz transition appears in systems with a small electron-electron correlation and large hybridization. We show that this situation is realized in 5d distorted perovskites with half-filled t2g bands such as NaOsO3, where the strong p-d hybridization reduces the local moment, and spin-orbit coupling causes a large renormalization of the electronic mobility. This weakens the role of electronic correlations and drives the system towards an itinerant magnetic regime which enables spin fluctuations.