The Fermi surface of Sr2RuO4: spin-orbit and anisotropic Coulomb interaction effects

TL;DR

This study reveals that anisotropic Coulomb interactions are crucial for accurately modeling the Fermi surface of Sr2RuO4, highlighting the importance of many-body effects and spin-orbital entanglement in correlated multi-orbital systems.

Contribution

It demonstrates that Coulomb anisotropy significantly influences the Fermi surface, challenging the adequacy of isotropic Coulomb models and emphasizing the role of many-body effects in Sr2RuO4.

Findings

Coulomb anisotropy is essential for matching experimental Fermi surface data.

Low-energy self-energy differs from static Hartree-Fock predictions.

Strong spin-orbital entanglement affects pairing descriptions.

Abstract

The topology of the Fermi surface of Sr2RuO4 is well described by local-density approximation calculations with spin-orbit interaction, but the relative size of its different sheets is not. By accounting for many-body effects via dynamical mean-field theory, we show that the standard isotropic Coulomb interaction alone worsens or does not correct this discrepancy. In order to reproduce experiments, it is essential to account for the Coulomb anisotropy. The latter is small but has strong effects; it competes with the Coulomb-enhanced spin-orbit coupling and the isotropic Coulomb term in determining the Fermi surface shape. Its effects are likely sizable in other correlated multi-orbital systems. In addition, we find that the low-energy self-energy matrix -- responsible for the reshaping of the Fermi surface -- sizably differ from the static Hartree-Fock limit. Finally, we find a strong spin-orbital {entanglement}; this supports the view that the conventional description of Cooper pairs via factorized spin and orbital part might not apply to Sr2RuO4.