High-Resolution Photoemission on Sr2RuO4 Reveals Correlation-Enhanced Effective Spin-Orbit Coupling and Dominantly Local Self-Energies

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 β and γ 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. * present address: ISIS Facility, Rutherford

Imaginary-time matrix product state impurity solver in a real material calculation: Spin-orbit coupling in Sr2RuO4

“…4. This is in agreement with previous studies at higher temperature showing that interactions lead to approximately constant off-diagonal terms in the self-energy which can be interpreted as an effective enhancement of the SOC [12][13][14][15]…”

“…Meanwhile, the interplay of SOC and electronic correlations has become a current topic of research [12][13][14][15]. Theoretical predictions of an effective enhancement of the SOC due to electronic correlations by as much as a factor of two [12] have been quantified [13,14] by realistic DFT plus dynamical meanfield theory (DMFT) calculations [16,17] and recently confirmed experimentally [15]. The emerging picture is that SOC changes the electronic structure significantly at wave-vectors where nearly degenerate states are found in its absence, but at the same time leaves the overall correlation-induced renormalizations approximately unchanged.…”

Spin-orbit coupling and spin-triplet pairing symmetry in Sr2RuO4

“…The effect of SOC on the normal state Fermi surface (FS) has been emphasized previously in Ref. 16 and was recently found to be larger than previously thought 17 . However, the effect of SOC on the superconducting state is still poorly understood.…”

“…Chiral edge currents have been predicted for the chiral pwave pairing state but not detected 10,11 ; splitting of the superconducting transition temperature T c in the presence of an in-plane magnetic field or a uniaxial strain 12,13 is expected but not found. Recent NMR experiments 14,15 report a significant drop of the spin susceptibility in the superconducting phase measured in an in-plane magnetic field, which contradicts previous measurements 2 and suggest either spin-triplet helical or singlet pairing, although strong spin-orbit coupling 16,17 can complicate the interpretation of the experimental data.…”

Strongly Correlated Materials from a Numerical Renormalization Group Perspective: How the Fermi-Liquid State of Sr2RuO4 Emerges

“…3(a) below, reflecting the quasi-2D tetragonal crystal structure of Sr 2 RuO 4 , with quasi-2D xy orbitals and a strongly one-dimensional character of the degenerate xz/yz orbitals. We employ the same Wannier Hamiltonian as in [39,40,48] (without spin-orbit coupling) combined with a local Kanamori interaction [2,49] parametrized by U = 2.3 and J = 0.4 [24]. Throughout this work, we use eV = 1 as unit of energy if not otherwise indicated.…”