Ab-Initio Calculation of Quasiparticle Interference in Sr₂RuO₄

Quasiparticle interference (QPI) imaging of multiband materials with a two-dimensional electronic structure has been instrumental in the study of low-energy states and in capturing details of multiband ordering in these systems. Unbiased ab-initio calculation of quasiparticle interference from a microscopic model enables the study of parameters such as band structure, spin-orbit coupling (SOC) and Hund’s interaction on the superconducting order and allows comparison to the experimental QPI observed in the Ruthenates. To this end we utilize the functional renormalization group (fRG) to construct an unbiased self-energy for a three band model of the Ruthenates with a broken pseudospin symmetry. We find the interplay between the SOC and Hund’s coupling to be the primary driver of patterns in the measured QPI of the Ruthernates. Further, by varying the level of doping in the model, the fRG allows for an accounting of the role played by the Van Hove singularity in the superconducting state observed in Sr₂RuO₄.