BiCh2-based superconductors have a stacking structure with a conducting layer composed of Bi and Ch (Ch=S, Se) ions and an insulating layer consisting of Ln and O ions. LaO0.5F0.5BiS2, belonging to these superconductors, shows superconductivity at about 3 K [1]. Furthermore, Pb substitution for partial Bi ions induces the superconducting transition temperature (Tc) to about 5 K at LaO0.5F0.5Bi0.9Pb0.1S2 and a structural phase transition at about 150 K [2,3]. Therefore, the relationship between Tc and the structural phase transition temperature (Tano) is crucial for understanding the superconducting mechanism. So far, we have synthesized La1-xSrxO0.5F0.5Bi0.9Pb0.1S2 single crystals, where Sr ions are partially substituted for La ion and characterized their physical properties to investigate this relationship. As a result, Tc decreased while Tano increased with increasing Sr substitution. On the other hand, details of the crystal structure with Sr substitution have yet to be clarified.
In this study, we performed a single-crystal structure analysis for LaO0.5F0.5Bi0.9Pb0.1S2 substituted for Sr ion by using synchrotron X-ray diffraction measurements and determined the detailed structure. In the talk, we will discuss the structural changes at the atomic displacement level by Sr substitution and their relation to Tc and Tano.
[1] Y. Mizuguchi et al. J. Phys. Soc. Jpn 81, 114725 (2012).
[2] S. Otsuki et. al. Solid State Commun. 270, 17-21 (2018).
[3] S.Okada et. al. J. Phys. Soc. Jpn. 93, 064701 (2024).
Keywords: Element Substitution, BiS2-based Superconductors, Structure analysis, Single crystals growth