Electronic and crystal structures ofFeAsOH(= La, Sm) studied by x-ray absorption spectroscopy, x-ray emission spectroscopy, and x-ray diffraction (part I: carrier-doping dependence).

A carrier doping by a hydrogen substitution in LaFeAsOHis known to cause two superconducting (SC) domes with the magnetic order at both end sides of the doping. In contrast, SmFeAsOHhas a similar phase diagram but shows single SC dome. Here, we investigated the electronic and crystal structures for iron oxynitrideFeAsOH(= La, Sm) with the range of= 0-0.5 by using x-ray absorption spectroscopy, x-ray emission spectroscopy, and x-ray diffraction. For both compounds, we observed that the pre-edge peaks of x-ray absorption spectra near the Fe-edge were reduced in intensity on doping. The character arises from the weaker As-Fe hybridization with the longer As-Fe distance in the higher doped region. We can reproduce the spectra near the Fe-edge according to the Anderson impurity model with realistic valence structures using the local-density approximation (LDA) plus dynamical mean-field theory (DMFT). For= Sm, the integrated-absolute difference (IAD) analysis from x-ray Fe-emission spectra increases significantly. This is attributed to the enhancement of magnetic moment of Fe 3electrons stemming from the localized picture in the higher doped region. A theoretical simulation implementing the self-consistent vertex-correction method reveals that the single dome superconducting phase for= Sm arises from a better nesting condition in comparison with= La.