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arxiv: 1906.11090 · v2 · pith:3SWD2D7Gnew · submitted 2019-06-26 · ❄️ cond-mat.supr-con

Nanoscale Interlayer Defects in Iron Arsenides

Qiang Zheng , Miaofang Chi , Maxim Ziatdinov , 2 Li Li , Petro Maksymovych , Matt F. Chisholm , 1 Sergei V. Kalinin , Athena S. Sefat This is my paper

Pith reviewed 2026-05-25 15:02 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con
keywords BaFe2As2iron arsenidesstacking faultsinterlayer defectshigh-Tc superconductivitypercolationmicroscopy
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The pith

Nanoscale stacking faults in BaFe2As2 separate ordered domains without reducing the superconducting transition temperature.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper reports discovery of nanoscale interlayer defects along the c-direction in BaFe2As2 using local real-space microscopy. Ordered 122 arrangements appear in the ab-plane and in 10-20 nm regions perpendicular to it, with Ba ions displaced to form stacking faults that separate adjacent ordered domains while the FeAs substructure stays rigid. The authors conclude that these localized interlayer defects have minimal connection to high-temperature superconductivity, as Cooper pairs can follow percolative paths through the continuous ordered 122 lattice without affecting Tc. This matters for understanding how chemical disorder between planes influences layered superconductors.

Core claim

Using a local real-space microscopy probe, evidence is found of nanoscale interlayer defects along the c-crystallographic direction in BaFe2As2 based iron-arsenide superconductors. Ordered 122 atomic arrangements exist within the ab-plane and within regions of ~10 to 20 nm size perpendicular to this plane. While the FeAs substructure is very rigid, Ba ions are relatively weakly bound and can be displaced from the 122, forming stacking faults resulting in the physical separation of the 122 between adjacent ordered domains. The Cooper pairs may be finding a way around such localized interlayer defects through a percolative path of the ordered layered 122 lattice that may not affect Tc.

What carries the argument

percolative path through the ordered layered 122 lattice that allows Cooper pairs to bypass localized interlayer stacking faults formed by displaced Ba ions

If this is right

  • Interlayer chemical disorder in the form of Ba-displacement stacking faults does not measurably suppress Tc.
  • The FeAs planes remain rigid while Ba ions move to create the separating faults.
  • Superconductivity continues via percolation through continuous regions of the ordered 122 lattice.
  • The connection between such interlayer disorder and high-temperature superconductivity is minimal in 122 iron arsenides.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Similar stacking faults may exist in related 122 compounds but remain undetected if they leave Tc unchanged.
  • The 10-20 nm domain size could indicate the minimum length scale required for effective percolation of superconducting order.
  • Control of Ba binding during growth might allow deliberate introduction or removal of these defects.

Load-bearing premise

The microscopy images are correctly interpreted as Ba-ion displacements that form stacking faults separating ordered 122 domains, and that these defects do not measurably suppress Tc.

What would settle it

Observation that Tc decreases measurably as the density of these stacking faults increases across samples, or direct confirmation that the imaged features are not stacking faults.

read the original abstract

Using a local real-space microscopy probe, we discover evidence of nanoscale interlayer defects along the c-crystallographic direction in BaFe2As2 (122) based iron-arsenide superconductors. We find ordered 122 atomic arrangements within the ab-plane, and within regions of ~10 to 20 nm size perpendicular to this plane. While the FeAs substructure is very rigid, Ba ions are relatively weakly bound and can be displaced from the 122, forming stacking faults resulting in the physical separation of the 122 between adjacent ordered domains. The evidence for interlayer defects between the FeAs superconducting planes gives perspective on the minimal connection between interlayer chemical disorder and high-temperature superconductivity. In particular, the Cooper pairs may be finding a way around such localized interlayer defects through a percolative path of the ordered layered 122 lattice that may not affect Tc.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript reports the discovery, via local real-space microscopy, of nanoscale interlayer defects along the c-axis in BaFe2As2 (122) iron-arsenide superconductors. Ordered 122 atomic arrangements are observed within the ab-plane and within ~10–20 nm domains perpendicular to it; the FeAs substructure is described as rigid while Ba ions are displaced from ideal 122 positions to form stacking faults that physically separate ordered domains. The authors conclude that these interlayer defects have only a minimal connection to high-Tc superconductivity because Cooper pairs can follow percolative paths through the ordered 122 lattice without measurable Tc suppression.

Significance. If the defect assignment is robustly confirmed, the work supplies a concrete real-space example of how localized interlayer chemical disorder can coexist with high-Tc superconductivity in the 122 family, thereby constraining models that tie Tc directly to interlayer coherence or chemical order.

major comments (2)
  1. [Abstract / microscopy results] Abstract and results description: the assignment of observed contrast to Ba-ion displacements that create stacking faults separating ordered 122 domains is presented without quantitative image simulation, complementary chemical mapping (e.g., EDX/EELS), or statistical comparison to alternative defect models or imaging artifacts. This identification is load-bearing for both the existence of the claimed interlayer defects and the subsequent percolative-path argument.
  2. [Abstract] Abstract: no quantitative metrics (defect density, displacement amplitudes, error bars), error analysis, sample-preparation details, or direct Tc measurements on the imaged regions are supplied, leaving the claim that the defects “may not affect Tc” without direct experimental anchor.
minor comments (1)
  1. [Abstract] The abstract paragraph describing the percolative-path scenario would benefit from a brief statement of the length scale over which the ordered domains are claimed to remain connected.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the careful and constructive review of our manuscript on nanoscale interlayer defects in BaFe2As2. We address each major comment below and indicate planned revisions where appropriate to strengthen the presentation of the microscopy results and supporting arguments.

read point-by-point responses

  1. Referee: [Abstract / microscopy results] Abstract and results description: the assignment of observed contrast to Ba-ion displacements that create stacking faults separating ordered 122 domains is presented without quantitative image simulation, complementary chemical mapping (e.g., EDX/EELS), or statistical comparison to alternative defect models or imaging artifacts. This identification is load-bearing for both the existence of the claimed interlayer defects and the subsequent percolative-path argument.

    Authors: The assignment of contrast to Ba displacements follows from the observed atomic-scale images showing rigid FeAs layers with interruptions and shifts consistent with the weaker binding of Ba in the 122 structure. We agree that quantitative image simulations, statistical comparisons to alternative models or artifacts, and additional analysis would strengthen the claim. These will be added to the revised manuscript, including simulations of expected contrast for Ba displacements versus other possibilities and analysis across multiple images. revision: yes

  2. Referee: [Abstract] Abstract: no quantitative metrics (defect density, displacement amplitudes, error bars), error analysis, sample-preparation details, or direct Tc measurements on the imaged regions are supplied, leaving the claim that the defects “may not affect Tc” without direct experimental anchor.

    Authors: Quantitative metrics such as defect density and displacement amplitudes with error bars, along with expanded error analysis and sample-preparation details, will be added to the revised manuscript. Direct Tc measurements on the exact imaged nanoscale regions are not available, as the work uses local microscopy on samples prepared for imaging rather than combined transport measurements; the percolative-path conclusion rests on the observed domain connectivity and the material's established high Tc. The abstract will be revised to clarify the indirect nature of this evidence. revision: partial

standing simulated objections not resolved
  • Direct Tc measurements localized to the specific nanoscale regions examined by microscopy, which would require specialized integrated techniques not employed in the study.

Circularity Check

0 steps flagged

No circularity in experimental microscopy report

full rationale

This is a purely observational experimental paper reporting real-space microscopy images of BaFe2As2. It contains no equations, fitted parameters, predictions, derivations, or theoretical claims that could reduce to their own inputs. The abstract and described findings present direct image interpretations of defect structures and their possible relation to Tc, without any self-referential fitting, self-citation load-bearing steps, or ansatz smuggling. The derivation chain is absent, so the paper is self-contained against its own imaging data as external benchmark.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The claim depends on standard interpretation of scanning-probe images as faithful atomic maps and on the assumption that the observed defects are stacking faults caused by Ba displacement.

axioms (1)
  • domain assumption Scanning probe microscopy images accurately reflect local atomic positions and displacements in the 122 structure.
    Invoked when mapping observed contrast to Ba-ion shifts and stacking faults.

pith-pipeline@v0.9.0 · 5705 in / 1185 out tokens · 31287 ms · 2026-05-25T15:02:15.433142+00:00 · methodology

discussion (0)

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Reference graph

Works this paper leans on

22 extracted references · 22 canonical work pages

  1. [1]

    Rotter, M

    M. Rotter, M. Tegel and D. Johrendt, Phys. Rev. Lett. 101 (2008), 107006

    work page 2008

  2. [2]

    A. S. Sefat, R. Jin, M. A. McGuire, B. C. Sales, D. J. Singh and D. Mandrus, Phys. Rev. Lett. 101, (2008), 117004

    work page 2008

  3. [3]

    Z. Wang, Y. J. Song, H. L. Shi, Z. W. Wang, Z. Chen, H. F. Tian, G. F. Chen, J. G. Guo, H. X. Yang and J. Q. Li, Phys. Rev. B 83 (2011),140505

    work page 2011

  4. [4]

    Cortes-Gil, D

    R. Cortes-Gil, D. R. Parker, M. J. Pitcher, J. Hadermann and S. J. Clarke, Chem. Mater. 22 (2010), 4304

    work page 2010

  5. [5]

    S. M. Kazakov, A. M. Abakumov, S. González, J. M. Perez -Mato, A. V. Ovchinnikov, M. V. Roslova, A. I. Boltalin, I. V. Morozov, E. V. Antipov and G. Van Tendeloo, Chem. Mater. 23 (2011), 4311

    work page 2011

  6. [6]

    Cantoni, M

    C. Cantoni, M. A. McGuire, B. Saparov, A. F. May, T. Keiber, F. Bridges, A. S. Sefat and B. C. Sales, Adv. Mater., 27 (2015), 2715

    work page 2015

  7. [7]

    Cantoni, A

    C. Cantoni, A. F. May, J. E. Mitchell, A. S. Sefat, M. A. McGuire and B. C. Sales, Microsc. Microanal. 19 (2013), 340

    work page 2013

  8. [8]

    H. Cao, C. Cantoni, A. F. May, M. A. McGuire, B. C. Chakoumakos, S. J. Pennycook, R. Custelcean, A. S. Sefat and B. C. Sales, Phys. Rev. B 85 (2012), 054515

    work page 2012

  9. [9]

    Z. Wang, Y. Cai, H.-X. Yang, H.-F. Tian, Z.-W. Wang, C. Ma, Z. Chen and J.-Q. Li, Chin. Phys. B. 22 (2013), 087409

    work page 2013

  10. [10]

    R. C. Che, F. Han, C. Y. Liang, X. B. Zhao and H. H. Wen, Phys. Rev. B 90 (2014),104503

    work page 2014

  11. [11]

    M. P. Allan, T. M. Chuang, F. Massee, Y. Xie, N. Ni, S. L. Bud’ko, G. S. Boebinger, Q. Wang, D. S. Dessau, P. C. Canfield, M. S. Golden and J. C. Davis, Nat. Phys. 9 (2013), 220

    work page 2013

  12. [12]

    W. D. Wise, K. Chatterjee, M. C. Boyer, T. Kondo, T. Takeuchi, H. Ikuta, Z. Xu, J. Wen, G. D. Gu, Y. Wang and E. W. Hudson, Nat. Phys. 5 (2009), 213

    work page 2009

  13. [13]

    Gofryk, M

    K. Gofryk, M. Pan, C. Cantoni, B. Saparov, J. E. Mitchell and A. S. Sefat, Phys. Rev. Lett. 112 (2014), 047005

    work page 2014

  14. [14]

    C. Ma, H. X. Yang, H. F. Tian, H. L. Shi, J. B. Lu, Z. W. Wang, L. J. Zeng, G. F. Chen, N. L. Wang and J. Q. Li, Phys. Rev. B 79 (2009), 060506

    work page 2009

  15. [15]

    Saparov, C

    B. Saparov, C. Cantoni, M. Pan, T. C. Hogan, W. R. Ii, S. D. Wilson, K. Fritsch, B. D. Gaulin and A. S. Sefat, Scientific Reports 4 (2014), 4120

    work page 2014

  16. [16]

    A. S. Sefat, Curr. Opin. Solid State Mater. Sci. 17 (2013), 59

    work page 2013

  17. [17]

    L. Li, H. Cao, M. A. McGuire, J. S. Kim, G. R. Stewart and A. S. Sefat, Phys. Rev. B 92 (2015), 094504

    work page 2015

  18. [18]

    Cantoni, J

    C. Cantoni, J. E. Mitchell, A. F. May, M. A. McGuire, J.-C. Idrobo, T. Berlijn, E. Dagotto, M. F. Chisholm, W. Zhou, S. J. Pennycook, A. S. Sefat, B. C. Sales, Adv. Mater. 26 (2014), 6193

    work page 2014

  19. [19]

    V Zaikina, M

    J. V Zaikina, M. Batuk, A. M. Abakumov, A. Navrotsky, S. M. Kauzlarich, J. Am. Chem. Soc. 136 (2014), 16932

    work page 2014

  20. [20]

    P. K. Suri, J. Yan, D. G. Mandrus, D. J. Flannigan, J. Phys. Chem. C 120 (2016), 18931

    work page 2016

  21. [21]

    P. Yuan, Z. Xu, D. Wang, M. Zhang, J. Li, Y. Ma, Super. Sci. Tech. 30 (2017), 025001

    work page 2017

  22. [22]

    Trommler, J

    S. Trommler, J. Hanisch, V Matias, R. Huhne, E. Reich, K. Iida, S. Haindl, L. Schultz, B. Holzapfel, Super. Sci. Tech. 25 (2012), 084019. 8 ACKNOWLEDGEMENT This manuscript has been authored by UT -Battelle, LLC under Contract No. DE -AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the...

    work page 2012