Local structure displacements in La1−xCexOBiSSe as a function of Ce substitution. (December 2020)

• Record Type: Journal Article
• Authors: Pugliese, G.M.; Stramaglia, F.; Capone, F.G.; Hacisalihoglu, M.Y.; Kiyama, R.; Sogabe, R.; Goto, Y.; Pollastri, S.; De Souza, D. Oliveira; Olivi, L.; Mizokawa, T.; Mizuguchi, Y.; Saini, N.L.
• Is Part Of: Journal of physics and chemistry of solids. Volume 147(2020)
• Publication Date: 2020-12
• Subjects: BiS2-based systems -- Superconductivity -- Self-doping -- Local structure; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2020.109648
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: We have investigated the local structure of layered La 1 − x Ce x OBiSSe system by Bi L 3 -edge extended X-ray absorption fine structure (EXAFS) measurements for different Ce substitutions. Ce L 3 -edge X-ray absorption spectroscopy (XAS) has been used to evaluate the Ce valence responsible for the self-doping in this system. We have found that the local distortion, determined by the separation between two Bi-Ch distances within the BiCh 2 -layer (Ch=S, Se), is quickly suppressed by Ce substitution while the axial Bi-S2 bond elongates. Ce L 3 -edge XAS reveals a coexistence of Ce 3 + and Ce 4 + in which the Ce 4 + weight decreases, an indication of a partial breaking of R E -S-Bi ( R E =La/Ce) charge transfer channel with Ce substitution. The results suggest that interaction between R E O spacer layer and BiCh 2 layer, dictated by the out-of-plane Bi-S2 distance, has a significant role in triggering superconductivity in the title system, with the in-plane distortion controlling the charge mobility within the BiCh 2 -layer. Highlights: The effect of Ce substitution in BiCh 2 - based superconductor has been studied. The local structure of BiCh 2 - layer changes significantly by Ce substitution. The mixed valence of Ce is responsible for the self-doping of the BiCh 2 - layer. The BiCh 2 distortion is suppressed and the axial Bi-Ch distance elongates. The axial distance controls the charge transfer to triggers the superconductivity.