Correlated disorder-to-order crossover in the local structure of KxFe2-ySe2-zSz

Mangelis P, Koch RJ, Lei H, Neder R, Mcdonnell MT, Feygenson M, Petrovic C, Lappas A, Bozin ES (2019)

Publication Type: Journal article

Publication year: 2019

Journal

Physical Review B American Physical Society

Book Volume: 100

Journal Issue: 9

DOI: 10.1103/PhysRevB.100.094108

Abstract

A detailed account of the local atomic structure and disorder at 5 K across the phase diagram of the high-temperature superconductor KxFe2-ySe2-zSz (0 <= z <= 2) is obtained from neutron total scattering and associated atomic pair distribution function (PDF) approaches. Various model-independent and model-dependent aspects of the analysis reveal a high level of structural complexity on the nanometer length scale. Evidence is found for considerable disorder in the c-axis stacking of the FeSe1-xSx slabs without observable signs of turbostratic character of the disorder. In contrast to the related FeCh (Ch = S, Se)-type superconductors, substantial Fe-vacancies are present in KxFe2-ySe2-zSz, deemed detrimental for superconductivity when ordered. Our study suggests that the distribution of vacancies significantly modifies the iron-chalcogen bond-length distribution, in agreement with observed evolution of the PDF signal. A crossoverlike transition is observed at a composition of z approximate to 1, from a correlated disorder state at the selenium end to a more vacancy-ordered (VO) state closer to the sulfur end of the phase diagram. The S-content-dependent measures of the local structure are found to exhibit distinct behavior on either side of this crossover, correlating well with the evolution of the superconducting state to that of a magnetic semiconductor toward the z approximate to 2 end. The behavior reinforces the idea of the intimate relationship of correlated Fe-vacancy order in the local structure and the emergent electronic properties.

Authors with CRIS profile

Reinhard Neder Professur für Allgemeine Mineralogie/Kristallographie

Involved external institutions

Foundation for Research and Technology-Hellas (FORTH) / Ίδρυμα Τεχνολογίας και Έρευνας GR Greece (GR) Brookhaven National Laboratory US United States (USA) (US) Oak Ridge National Laboratory US United States (USA) (US)

How to cite

APA:

Mangelis, P., Koch, R.J., Lei, H., Neder, R., Mcdonnell, M.T., Feygenson, M.,... Bozin, E.S. (2019). Correlated disorder-to-order crossover in the local structure of KxFe2-ySe2-zSz. Physical Review B, 100(9). https://doi.org/10.1103/PhysRevB.100.094108

MLA:

Mangelis, P., et al. "Correlated disorder-to-order crossover in the local structure of KxFe2-ySe2-zSz." Physical Review B 100.9 (2019).

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