Local-structure insight into the improved superconducting properties of Pb-substituted La(O, F)BiS2: a photoelectron holography study

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Abstract
Pb-substituted La(O, F)BiS2 (Pb-LaOFBiS2) exhibits improved superconducting properties and a resistivity anomaly around 100 K that is attributed to a structural transition. We have performed temperature(T)-dependent photoelectron holography (PEH) to study dopant incorporation sites and the local structure change across the anomaly. The PEH study of Pb-LaOFBiS2 provided evidence for the dominant incorporation sites of Pb and F: Pb atoms are incorporated into the Bi sites and F atoms are incorporated into the O site. No remarkable difference in the local structures around Pb and Bi atoms was observed. Across the temperature of the resistivity anomaly (T *), photoelectron holograms of Bi 4f changed. Comparisons of holograms with those of non-substituted LaOFBiS2 sample, as well as simulated holograms, suggested that (1), above T *, the tetragonal structure of Pb-LaOFBiS2 is different from the tetragonal structure of LaOFBiS2 and (2), below T *, the tetragonal structure still remains in Pb-LaOFBiS2. We discuss a possible origin of the difference in the structure above T * and the implication of the result below T *, which are necessary ingredients to understand the physical properties of Pb-LaOFBiS2.
Funding Information
  • the Research Project of Tianshui Normal University (PTJ2023-05; PTJ2023-02)
  • Experiments at SPring-8 were performed (2021B1027, 2021B3845, 2022A3845, and 2022B1735., 2021B1027, 2021B3845, 2022A3845, and 2022B1735.)
  • the JAEA Advanced Characterization Nanotechnology Platform under the “Nanotechnology Platform” of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan (JPMXP09A21AE23 and JPMXP09A21BE23, JPMXP09A21AE23 and JPMXP09A21BE23)
  • The Program for Promoting the Enhancement of Research Universities. (JSPS KAKENHI Grant Numbers (JP18KK0076, JP20K20522, and JP20H05882))

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