La-doping effect on spin-orbit coupled Sr2IrO4 probed by x-ray absorption spectroscopy

Abstract

Sr2IrO4 was predicted to be an unconventional superconductor upon carrier doping since it highly resembles the high-temperature cuprates. Here, to understand carrier doping effect on spin-orbit coupled Mott insulator Sr2IrO4, the electronic structure and local structure distortion for Sr2-xLaxIrO4 system have been investigated by x-ray absorption spectroscopy (XAS). By comparing the intensity of white-line features at the Ir L2,3 absorption edges, we observe remarkably large branching ratios in La-doped compounds, greater than that of the parent material Sr2IrO4, suggesting a strong spin-orbit interaction (SOI) for Sr2IrO4-based system. Moreover, extended x-ray absorption fine structure (EXAFS) spectra demonstrate more regular IrO6 octahedra, i.e. the weakened crystal electric field (CEF) versus La-doping. By theoretical calculations, the synergistic effect of regular IrO6 octahedra and electron doping is established, which accounts for the transition from a Mott insulator to a conductive state in Sr2-xLaxIrO4-based system.

14 pages, 6 figures. arXiv admin note: text overlap with arXiv:1610.09817

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Cited by in corpus (4)

• Square Lattice Iridates
• Influence of multiplet structure on photoemission spectra of spin-orbit driven Mott insulators: application to $\mathbf{S}{\mathbf{r}}_2\mathbf{Ir}{\mathbf{O}}_4$
• Electronic and optical properties of La-doped Sr${}_3$Ir${}_2$O${}_7$ epitaxial thin-films
• Possible superconductivity induced by a large spin-orbit coupling in carrier doped iridium oxide insulators: A weak coupling approach