Electronic structures of layered perovskite Sr2MO4 (M=Ru, Rh, and Ir)

TL;DR

This study explores the electronic structures of layered Sr2MO4 compounds with M=Ru, Rh, Ir, revealing similar optical features despite different ground states, and highlights large e_g orbital splittings due to extended d orbitals.

Contribution

It provides detailed optical and x-ray absorption data showing common electronic structures in 4d and 5d layered oxides, emphasizing the large orbital energy splittings.

Findings

Similar interband transitions in optical spectra across compounds

Large e_g orbital energy splitting (~2 eV)

Electronic properties influenced by crystal structure and orbital extension

Abstract

We investigated the electronic structures of the two-dimensional layered perovskite Sr$_{2}$\textit{M}O$_{4}$ (\textit{M}=4\textit{d} Ru, 4\textit{d} Rh, and 5\textit{d} Ir) using optical spectroscopy and polarization-dependent O 1\textit{s} x-ray absorption spectroscopy. While the ground states of the series of compounds are rather different, their optical conductivity spectra $\sigma(\omega)$ exhibit similar interband transitions, indicative of the common electronic structures of the 4\textit{d} and 5\textit{d} layered oxides. The energy splittings between the two $e_{g}$ orbitals, $i.e.$, $d_{3z^{2}-r^{2}}$ and $d_{x^{2}-y^{2}}$, are about 2 eV, which is much larger than those in the pseudocubic and 3\textit{d} layered perovskite oxides. The electronic properties of the Sr$_{2}$\textit{M}O$_{4}$ compounds are discussed in terms of the crystal structure and the extended character of the 4\textit{d} and 5\textit{d} orbitals.