Temperature dependent local atomic displacements in ammonia intercalated iron selenide superconductor
Paris, E. (Istituto Italiano di Tecnologia)
Simonelli, Laura (ALBA Laboratori de Llum de Sincrotró)
Wakita, Takanori (Okayama University)
Marini, Carlo (ALBA Laboratori de Llum de Sincrotró)
Lee, J. H. (Okayama University)
Olszewski, Wojciech (University of Bialystok)
Terashima, Kensei (Okayama University)
Kakuto, Takeshi (Okayama University)
Nishimoto, N. (Okayama University)
Kimura, T. (Okayama University)
Kudo, Kazutaka (Okayama University)
Kambe, Takashi (Okayama University)
Nohara, Minoru (Okayama University)
Yokoya, Takayoshi (Okayama University)
Saini, Naurang L. (Sapienza Universitá di Roma)

Data:	2016
Resum:	Recently, ammonia-thermal reaction has been used for molecular intercalation in layered FeSe, resulting a new Li x (NH 3) y Fe 2 Se 2 superconductor with T c ∼ 45 K. Here, we have used temperature dependent extended x-ray absorption fine structure (EXAFS) to investigate local atomic displacements in single crystals of this new superconductor. Using polarized EXAFS at Fe K-edge we have obtained direct information on the local Fe-Se and Fe-Fe bondlengths and corresponding mean square relative displacements (MSRD). We find that the Se-height in the intercalated system is lower than the one in the binary FeSe, suggesting compressed FeSe 4 tetrahedron in the title system. Incidentally, there is hardly any effect of the intercalation on the bondlengths characteristics, revealed by the Einstein temperatures, that are similar to those found in the binary FeSe. Therefore, the molecular intercalation induces an effective compression and decouples the FeSe slabs. Furthermore, the results reveal an anomalous change in the atomic correlations across T c, appearing as a clear decrease in the MSRD, indicating hardening of the local lattice mode. Similar response of the local lattice has been found in other families of superconductors, e. g. , A15-type and cuprates superconductors. This observation suggests that local atomic correlations should have some direct correlation with the superconductivity.
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Publicat a:	Scientific reports, Vol. 6 (June 2016) , art. 27646, ISSN 2045-2322

DOI: 10.1038/srep27646
PMID: 27276997

8 p, 1.1 MB

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