Electron dichotomy on the SrTiO3 defect surface augmented by many-body effects

In a common paradigm, the electronic structure of condensed matter is divided into weakly and strongly correlated compounds. While conventional band theory usually works well for the former class, many-body effects are essential for the latter. Materials such as the familiar SrTiO3 (STO) compound that bridge or even abandon this characterization scheme are highly interesting. Here, it is shown, by means of combining density functional theory with dynamical mean-field theory, that oxygen vacancies on the STO (001) surface give rise to a dichotomy of weakly correlated t2g low-energy quasiparticles and localized "in-gap" states of dominant eg character with a subtle correlation signature. We furthermore touch base with recent experimental work and study the surface instability towards magnetic order.