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

TL;DR

This study uses photoelectron holography to reveal how Pb and F substitutions affect the local structure and superconducting properties of La(O, F)BiS2.

Contribution

The paper provides new insights into the local structural changes and dopant incorporation in Pb-substituted La(O, F)BiS2 using temperature-dependent photoelectron holography.

Findings

Pb atoms are incorporated into Bi sites and F atoms into O sites in Pb-LaOFBiS2.

The tetragonal structure of Pb-LaOFBiS2 differs from LaOFBiS2 above the resistivity anomaly temperature (T*).

The tetragonal structure remains in Pb-LaOFBiS2 below T* despite the resistivity anomaly.

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.

The online version contains supplementary material available at 10.1038/s41598-025-86233-2.

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