Quasiparticles through the seasons: Theoretical insights from electronic Raman spectroscopy, ARPES and optical spectroscopy

The use of density functional theory (DFT) and dynamical mean field theory (DMFT) has proven successful as a combined approach for electronic structure calculations of strongly correlated materials. In this talk, I will present three recent advances in material-realistic calculations, focusing on the Hund metal Sr2RuO4.
First, I will discuss our calculation of the electronic Raman response within the DFT+DMFT framework using the effective mass approximation. This work provides a novel interpretation of the experimentally observed orbital dichotomy and highlights the importance of finite-frequency interband nesting. Second, I will address the signatures of quasiparticles at finite temperature. Contrary to earlier reports, our combined theoretical and experimental study demonstrates the existence of resilient quasiparticles in Sr2RuO4 even at high temperatures, which disappear upon reaching the bad metal state not by losing weight but via excessive broadening.
Lastly, I will discuss advances in overcoming numerical challenges associated with the DMFT embedding, focusing on our recent progress in computing Brillouin zone integrals, which are often limited in resolution due to increasing numerical complexity at lower temperatures and scattering rates. These advancements are important for next-generation quantum impurity solvers and the precise characterization of spectral features for low-temperature phenomena in condensed matter physics.