In this study, we investigate the bulk electronic structure of Pb-substituted LaO0.5F0.5BiS2 single crystals, using two types of hard-x-ray spectroscopy. High-energy-resolution fluorescence-detected x-ray absorption spectroscopy revealed a spectral change at low temperatures. Using density functional theory (DFT) simulations, we find that the temperature-induced change originates from a structural phase transition, similar to the pressure-induced transition in LaO0.5F0.5BiS2. This finding suggests that the mechanism of bulk superconductivity induced by Pb substitution is the same as that under high pressure. Furthermore, a novel low-valence state with a mixture of divalent and trivalent Bi ions is discovered using hard x-ray photoemission spectroscopy with the aid of DFT calculations.
@article{arxiv.2305.19622,
title = {Bulk superconductivity in Pb-substituted BiS$_{\bf 2}$-based compounds studied by hard-x-ray spectroscopy},
author = {A. Yamasaki and T. Oguni and T. Hayashida and K. Miyazaki and N. Tanaka and K. Nakagawa and K. Tamura and K. Mimura and N. Kawamura and H. Fujiwara and G. Nozue and A. Ose and Y. Kanai-Nakata and A. Higashiya and S. Hamamoto and K. Tamasaku and M. Yabashi and T. Ishikawa and S. Imada and A. Sekiyama and H. Sakata and S. Demura},
journal= {arXiv preprint arXiv:2305.19622},
year = {2024}
}