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Title: Formation mechanism of superconducting phase and its three-dimensional architecture in pseudo-single-crystal K xFe 2-ySe 2

Abstract

Here, we report how the superconducting phase forms in pseudo-single-crystal K xFe 2-ySe 2. In situ scanning electron microscopy (SEM) observation reveals that, as an order-disorder transition occurs, on cooling, most of the high-temperature iron-vacancy-disordered phase gradually changes into the iron-vacancy-ordered phase whereas a small quantity of the high-temperature phase retains its structure and aggregates to the stripes with more iron concentration but less potassium concentration compared to the iron-vacancy-ordered phase. The stripes that are generally recognized as the superconducting phase are actually formed as a remnant of the high-temperature phase with a compositional change after an “imperfect” order-disorder transition. It should be emphasized that the phase separation in pseudo-single-crystal K xFe 2-ySe 2 is caused by the iron-vacancy order-disorder transition. The shrinkage of the high-temperature phase and the expansion of the newly created iron-vacancy-ordered phase during the phase separation rule out the mechanism of spinodal decomposition proposed in an early report [Wang et al, Phys. Rev. B 91, 064513 (2015)]. Since the formation of the superconducting phase relies on the occurrence of the iron-vacancy order-disorder transition, it is impossible to synthesize a pure superconducting phase by a conventional solid state reaction or melt growth. By focused ion beam-scanning electronmore » microscopy, we further demonstrate that the superconducting phase forms a contiguous three-dimensional architecture composed of parallelepipeds that have a coherent orientation relationship with the iron-vacancy-ordered phase.« less

Authors:
 [1];  [1];  [2];  [3];  [4];  [5];  [2]
  1. Ames Lab., Ames, IA (United States)
  2. Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States)
  3. Carl Zeiss Microscopy, LLC, Peabody, MA (United States). Ion Microscopy Innovation Center (IMIC)
  4. Carl Zeiss Microscopy, LLC, Thornwood, NY (United States)
  5. Oxford Instruments America, Inc., Concord, MA (United States)
Publication Date:
Research Org.:
Ames Lab., Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1249341
Alternate Identifier(s):
OSTI ID: 1237792
Report Number(s):
IS-J-8950
Journal ID: ISSN 2469-9950; PRBMDO
Grant/Contract Number:  
AC02-07CH11358
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 93; Journal Issue: 6; 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

Liu, Yong, Xing, Qingfeng, Straszheim, Warren E., Marshman, Jeff, Pedersen, Pal, McLaughlin, Richard, and Lograsso, Thomas A. Formation mechanism of superconducting phase and its three-dimensional architecture in pseudo-single-crystal KxFe2-ySe2. United States: N. p., 2016. Web. doi:10.1103/PhysRevB.93.064509.
Liu, Yong, Xing, Qingfeng, Straszheim, Warren E., Marshman, Jeff, Pedersen, Pal, McLaughlin, Richard, & Lograsso, Thomas A. Formation mechanism of superconducting phase and its three-dimensional architecture in pseudo-single-crystal KxFe2-ySe2. United States. https://doi.org/10.1103/PhysRevB.93.064509
Liu, Yong, Xing, Qingfeng, Straszheim, Warren E., Marshman, Jeff, Pedersen, Pal, McLaughlin, Richard, and Lograsso, Thomas A. Thu . "Formation mechanism of superconducting phase and its three-dimensional architecture in pseudo-single-crystal KxFe2-ySe2". United States. https://doi.org/10.1103/PhysRevB.93.064509. https://www.osti.gov/servlets/purl/1249341.
@article{osti_1249341,
title = {Formation mechanism of superconducting phase and its three-dimensional architecture in pseudo-single-crystal KxFe2-ySe2},
author = {Liu, Yong and Xing, Qingfeng and Straszheim, Warren E. and Marshman, Jeff and Pedersen, Pal and McLaughlin, Richard and Lograsso, Thomas A.},
abstractNote = {Here, we report how the superconducting phase forms in pseudo-single-crystal KxFe2-ySe2. In situ scanning electron microscopy (SEM) observation reveals that, as an order-disorder transition occurs, on cooling, most of the high-temperature iron-vacancy-disordered phase gradually changes into the iron-vacancy-ordered phase whereas a small quantity of the high-temperature phase retains its structure and aggregates to the stripes with more iron concentration but less potassium concentration compared to the iron-vacancy-ordered phase. The stripes that are generally recognized as the superconducting phase are actually formed as a remnant of the high-temperature phase with a compositional change after an “imperfect” order-disorder transition. It should be emphasized that the phase separation in pseudo-single-crystal KxFe2-ySe2 is caused by the iron-vacancy order-disorder transition. The shrinkage of the high-temperature phase and the expansion of the newly created iron-vacancy-ordered phase during the phase separation rule out the mechanism of spinodal decomposition proposed in an early report [Wang et al, Phys. Rev. B 91, 064513 (2015)]. Since the formation of the superconducting phase relies on the occurrence of the iron-vacancy order-disorder transition, it is impossible to synthesize a pure superconducting phase by a conventional solid state reaction or melt growth. By focused ion beam-scanning electron microscopy, we further demonstrate that the superconducting phase forms a contiguous three-dimensional architecture composed of parallelepipeds that have a coherent orientation relationship with the iron-vacancy-ordered phase.},
doi = {10.1103/PhysRevB.93.064509},
url = {https://www.osti.gov/biblio/1249341}, journal = {Physical Review B},
issn = {2469-9950},
number = 6,
volume = 93,
place = {United States},
year = {2016},
month = {2}
}

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Cited by: 8 works
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Works referenced in this record:

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Influence of microstructure on superconductivity in KxFe2−ySe2 and evidence for a new parent phase K2Fe7Se8
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Fe-vacancy order and superconductivity in tetragonal  -Fe1-xSe
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Structural Phase Separation in K 0.8 Fe 1.6+ x Se 2 Superconductors
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High-resolution characterization of microstructural evolution in Rb x Fe 2 y Se 2 crystals on annealing
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Fe 57 Mössbauer study of magnetic ordering in superconducting K 0 . 80 Fe 1 . 76 Se 2 . 00 single crystals
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Phase separation in superconducting and antiferromagnetic Rb 0.8 Fe 1.6 Se 2 probed by Mössbauer spectroscopy
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    Works referencing / citing this record:

    Nanoscale electrodynamics of strongly correlated quantum materials
    journal, November 2016