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Title: Correlated disorder-to-order crossover in the local structure of K x Fe 2 - y Se 2 - z S z

Abstract

Here, a detailed account of the local atomic structure and disorder at 5 K across the phase diagram of the high-temperature superconductor K x Fe 2 - y Se 2 - z S z ( 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 $${\mathrm{FeSe}}_{1{-}x}{\mathrm{S}}_{x}$$ 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 $${\mathrm{K}}_{x}{\mathrm{Fe}}_{2{-}y}{\mathrm{Se}}_{2{-}z}{\mathrm{S}}_{z}$$ 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 ≈ 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 ≈ 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:
 [1]; ORCiD logo [2];  [2];  [3];  [4];  [4];  [2];  [1];  [2]
  1. Inst. of Electronic Structure and Laser (IESL) of the Foundation for Research and Technology – Hellas (FORTH), Heraklion (Greece)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
  3. Friedrich-Alexander-Univ. Erlangen-Nürnberg, Erlangen (Germany)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1560003
Alternate Identifier(s):
OSTI ID: 1562169
Report Number(s):
BNL-212045-2019-JAAM
Journal ID: ISSN 2469-9950; PRBMDO
Grant/Contract Number:  
SC0012704; AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 100; Journal Issue: 9; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Mangelis, P., Koch, R. J., Lei, H., Neder, R. B., McDonnell, M. T., Feygenson, M., Petrovic, C., Lappas, A., and Bozin, E. S. Correlated disorder-to-order crossover in the local structure of KxFe2-ySe2-zSz. United States: N. p., 2019. Web. doi:10.1103/PhysRevB.100.094108.
Mangelis, P., Koch, R. J., Lei, H., Neder, R. B., McDonnell, M. T., Feygenson, M., Petrovic, C., Lappas, A., & Bozin, E. S. Correlated disorder-to-order crossover in the local structure of KxFe2-ySe2-zSz. United States. doi:10.1103/PhysRevB.100.094108.
Mangelis, P., Koch, R. J., Lei, H., Neder, R. B., McDonnell, M. T., Feygenson, M., Petrovic, C., Lappas, A., and Bozin, E. S. Mon . "Correlated disorder-to-order crossover in the local structure of KxFe2-ySe2-zSz". United States. doi:10.1103/PhysRevB.100.094108.
@article{osti_1560003,
title = {Correlated disorder-to-order crossover in the local structure of KxFe2-ySe2-zSz},
author = {Mangelis, P. and Koch, R. J. and Lei, H. and Neder, R. B. and McDonnell, M. T. and Feygenson, M. and Petrovic, C. and Lappas, A. and Bozin, E. S.},
abstractNote = {Here, 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 ${\mathrm{FeSe}}_{1{-}x}{\mathrm{S}}_{x}$ 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 ${\mathrm{K}}_{x}{\mathrm{Fe}}_{2{-}y}{\mathrm{Se}}_{2{-}z}{\mathrm{S}}_{z}$ 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 ≈ 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 ≈ 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.},
doi = {10.1103/PhysRevB.100.094108},
journal = {Physical Review B},
number = 9,
volume = 100,
place = {United States},
year = {2019},
month = {9}
}

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This content will become publicly available on September 16, 2020
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