Bulk superconductivity in Pb-substituted BiS${}_2$-based compounds studied by hard-x-ray spectroscopy

Abstract

In this study, we investigate the bulk electronic structure of Pb-substituted LaO${}_{0.5}$F${}_{0.5}$BiS${}_2$ 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 LaO${}_{0.5}$F${}_{0.5}$BiS${}_2$. 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.

arXiv comment8 pages, 6 figures, 1 table

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