Electronic correlations and enhanced spin-orbit coupling in Sr₂RuO₄ determined from high-resolution laser-based ARPES.

We combine laser-based angle-resolved photoemission and dynamical mean-field theory calculations to study the interplay of electron-electron correlations and spin-orbit coupling (SOC) in the model Fermi liquid Sr₂RuO₄. Analyzing the experimental Fermi surface, we show that correlations enhance SOC by a factor of ∼2 over the bare value. We further reveal that the real part of the self-energy of the β and γ sheet is momentum dependent and strongly non-linear down to low energies, in contrast to widely held believes about the phenomenology of Fermi liquids. Introducing a new method to determine orbital self-energies from quasiparticle states with multi-orbital composition, we demonstrate that the anisotropy of the self-energy does not imply momentum dependent many-body interactions. The non-linearity of the self-energy is reproduced by single-site dynamical mean field theory, which provides strong evidence for a dominantly electronic origin of ‘kinks’ in the quasiparticle dispersion of Sr₂RuO₄.