Abstract
We explore the interplay of electron-electron correlations and spin-orbit coupling in the model Fermi liquid Sr2RuO4 using laser-based angle-resolved photoemission spectroscopy. Our precise measurement of the Fermi surface confirms the importance of spin-orbit coupling in this material and reveals that its effective value is enhanced by a factor of about two, due to electronic correlations. The self-energies for the $\beta$ and $\gamma$ sheets are found to display significant angular dependence. By taking into account the multi-orbital composition of quasiparticle states, we determine self-energies associated with each orbital component directly from the experimental data. This analysis demonstrates that the perceived angular dependence does not imply momentum-dependent many-body effects, but arises from a substantial orbital mixing induced by spin-orbit coupling. A comparison to single-site dynamical mean-field theory further supports the notion of dominantly local orbital self-energies, and provides strong evidence for an electronic origin of the observed non-linear frequency dependence of the self-energies, leading to `kinks' in the quasiparticle dispersion of Sr2RuO4.
Highlights
The layered perovskite Sr2RuO4 is an important model system for correlated electron physics
We explore the interplay of electron-electron correlations and spin-orbit coupling in the model Fermi liquid Sr2RuO4 using laser-based angle-resolved photoemission spectroscopy
Our precise measurement of the Fermi surface confirms the importance of spin-orbit coupling in this material and reveals that its effective value is enhanced by a factor of about 2, due to electronic correlations
Summary
The layered perovskite Sr2RuO4 is an important model system for correlated electron physics. Theoretical progress has been made recently in revealing the important role of the intra-atomic Hund’s coupling as a key source of correlation effects in Sr2RuO4 [18,20,35] In this context, much attention was devoted to the intriguing properties of the unusual state above TFL, which displays metallic transport with no signs of resistivity saturation at the Mott-Ioffe-Regel limit [36]. The experimentally determined real part of the selfenergy displays strong deviations from the low-energy Fermi-liquid behavior Σ0ðωÞ ∼ ωð1 − 1=ZÞ þ Á Á Á for binding energies jωj larger than about 20 meV These deviations are reproduced by our DMFT calculations, suggesting that the cause of these nonlinearities are local electronic correlations.
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