We have investigated the local structure of layered La1−xCexOBiSSe system by Bi L3-edge extended X-ray absorption fine structure (EXAFS) measurements for different Ce substitutions. Ce L3-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 BiCh2-layer (Ch=S,Se), is quickly suppressed by Ce substitution while the axial Bi-S2 bond elongates. Ce L3-edge XAS reveals a coexistence of Ce3+ and Ce4+ in which the Ce4+ weight decreases, an indication of a partial breaking of RE-S-Bi (RE=La/Ce) charge transfer channel with Ce substitution. The results suggest that interaction between REO spacer layer and BiCh2 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 BiCh2-layer.
Local structure displacements in La1−xCexOBiSSe as a function of Ce substitution / Pugliese, G. M.; Stramaglia, F.; Capone, F. G.; Hacisalihoglu, M. Y.; Kiyama, R.; Sogabe, R.; Goto, Y.; Pollastri, S.; De Souza, D. O.; Olivi, L.; Mizokawa, T.; Mizuguchi, Y.; Saini, N. L.. - In: JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS. - ISSN 0022-3697. - 147:(2020), pp. N/A-N/A. [10.1016/j.jpcs.2020.109648]
Local structure displacements in La1−xCexOBiSSe as a function of Ce substitution
Pollastri S.;
2020
Abstract
We have investigated the local structure of layered La1−xCexOBiSSe system by Bi L3-edge extended X-ray absorption fine structure (EXAFS) measurements for different Ce substitutions. Ce L3-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 BiCh2-layer (Ch=S,Se), is quickly suppressed by Ce substitution while the axial Bi-S2 bond elongates. Ce L3-edge XAS reveals a coexistence of Ce3+ and Ce4+ in which the Ce4+ weight decreases, an indication of a partial breaking of RE-S-Bi (RE=La/Ce) charge transfer channel with Ce substitution. The results suggest that interaction between REO spacer layer and BiCh2 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 BiCh2-layer.
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