Quasiparticle self-consistent GW calculation of Sr$_2$RuO$_4$ and SrRuO$_3$:

Abstract

Using quasiparticle self-consistent $GW$ calculations, we re-examined the electronic structure of Sr$_2$RuO$_4$ and SrRuO$_3$. Our calculations show that the correlation effects beyond the conventional LDA (local density approximation) and GGA (generalized gradient approximation) are reasonably well captured by QS$GW$ self-energy without any {\it ad hoc} parameter or any ambiguity related to the double-counting and the downfolding issues. While the spectral weight transfer to the lower and upper Hubbard band is not observed, the noticeable bandwidth reduction and effective mass enhancement are obtained. Important features in the electronic structures that have been debated over the last decades such as the photoemission spectra at around $-3$ eV in Sr$_2$RuO$_4$ and the half-metallicity for SrRuO$_3$ are discussed in the light of our QS$GW$ results and in comparison with the previous studies. The promising aspects of QS$GW$ are highlighted as the first-principles calculation method to describe the moderately correlated 4$d$ transition metal oxides along with its limitations.