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arxiv: 1907.09287 · v1 · pith:57WLFTYUnew · submitted 2019-07-22 · ❄️ cond-mat.supr-con · cond-mat.mtrl-sci

Enhanced superconductivity by Na doping in SnAs-based layered compound Na_(1+x)Sn_(2-x)As₂

Hao Yuwen , Yosuke Goto , Rajveer Jha , Akira Miura , Chikako Moriyoshi , Yoshihiro Kuroiwa , Tatsuma D. Matsuda , Yuji Aoki
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Yoshikazu Mizuguchi
This is my paper

Pith reviewed 2026-05-24 18:01 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con cond-mat.mtrl-sci
keywords superconductivitylayered compoundtin pnictideNa dopingantisite defecttransition temperatureNaSn2As2
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The pith

Sodium doping on the tin site raises the superconducting transition temperature of NaSn2As2 to 2.1 K.

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

The paper shows that controlled Na doping onto Sn sites in the layered compound Na1+xSn2-xAs2 increases the superconducting transition temperature. Prior samples exhibited Tc values scattered between 1.2 and 1.6 K, indicating strong sensitivity to composition. At x = 0.4 the transition reaches 2.1 K. First-principles calculations find that NaSn antisite defects are energetically preferred over other cation vacancies. The result supplies a concrete route to tune superconductivity in tin pnictide layers.

Core claim

Na-doping on the Sn site (Na1+xSn2-xAs2) is effective in enhancing superconductivity, leading to Tc = 2.1 K for x = 0.4. First-principles calculation indicates that such a doping, or NaSn antisite defects, is energetically favored over other cation vacancies.

What carries the argument

NaSn antisite defects, which first-principles calculations show are the lowest-energy cation defects and thereby enable the observed Tc enhancement.

If this is right

  • The same antisite-doping route can be applied to raise Tc in other layered tin pnictide superconductors.
  • Tc variation across earlier reports is attributable to uncontrolled non-stoichiometry.
  • Defect-energy calculations can guide further compositional tuning in this material family.

Where Pith is reading between the lines

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

  • The doping strategy may transfer to chemically related pnictides whose Tc is also limited by stoichiometry.
  • Mapping Tc versus x beyond 0.4 would reveal whether an optimum doping level exists.
  • Reproducible synthesis protocols are required before the higher Tc can be used in device contexts.

Load-bearing premise

The measured rise in Tc is produced directly by the introduced NaSn antisite defects rather than by other uncontrolled differences in sample preparation.

What would settle it

Synthesizing Na1.4Sn1.6As2 by a route that suppresses antisite formation and verifying whether Tc stays below 2.1 K would test the claimed causal link.

read the original abstract

Superconducting transition temperature (Tc) reported in SnAs-based layered compound NaSn$_2$As$_2$ varies from 1.2 to 1.6 K, implying that its superconductivity is critically sensitive to non-stoichiometry. Here, we demonstrate that Na-doping on the Sn site (Na$_{1+x}$Sn$_{2-x}$As$_2$) is effective in enhancing superconductivity, leading to Tc = 2.1 K for x = 0.4. First-principles calculation indicates that such a doping, or Na$_{\rm Sn}$ antisite defects, is energetically favored over other cation vacancies. Our results pave the way for increasing Tc of layered tin pnictide superconductors.

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

3 major / 1 minor

Summary. The manuscript claims that Na doping on the Sn site in NaSn2As2, forming Na1+xSn2-xAs2 with x=0.4, raises the superconducting Tc from the reported 1.2-1.6 K range to 2.1 K. First-principles calculations are presented to show that NaSn antisite defects are energetically favored over other cation defects, suggesting a route to enhance Tc in layered tin pnictide superconductors.

Significance. If the Tc enhancement can be reproducibly attributed to the controlled Na doping rather than uncontrolled sample variations, the work would demonstrate a practical doping approach for tuning superconductivity in SnAs-based layered compounds. The experimental-DFT combination is standard for the field, but the current presentation leaves the central attribution unverified.

major comments (3)
  1. [Abstract / Experimental section] Abstract and main text: The reported Tc = 2.1 K for x = 0.4 is stated without error bars, without raw resistivity or magnetization data, and without any sample characterization (e.g., XRD, EDS, or ICP-MS) to confirm actual composition or absence of secondary phases. This directly undermines the claim that the increase is caused by Na doping rather than synthesis differences.
  2. [Results / Discussion] Results section: The manuscript notes that Tc in the parent compound varies from 1.2 to 1.6 K due to non-stoichiometry but provides no comparative synthesis controls, phase-purity data, or multiple-batch measurements for the x = 0.4 specimen to isolate the effect of the intentional Na1+xSn2-x substitution.
  3. [Computational Methods / Results] DFT section: While the calculations indicate NaSn antisites are lower in energy than vacancies, there is no analysis of the solubility limit at x = 0.4 or of possible phase separation, which is required to link the defect energetics to the observed Tc enhancement.
minor comments (1)
  1. [Throughout] Notation for the doped formula Na1+xSn2-xAs2 should be used consistently in all figures and tables.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive comments, which help clarify the presentation of our results. We address each major comment below and indicate the revisions that will be incorporated.

read point-by-point responses

  1. Referee: [Abstract / Experimental section] Abstract and main text: The reported Tc = 2.1 K for x = 0.4 is stated without error bars, without raw resistivity or magnetization data, and without any sample characterization (e.g., XRD, EDS, or ICP-MS) to confirm actual composition or absence of secondary phases. This directly undermines the claim that the increase is caused by Na doping rather than synthesis differences.

    Authors: We agree that the current presentation lacks sufficient experimental detail to firmly attribute the Tc increase to the intentional doping. In the revised manuscript we will add error bars to the reported Tc value, include the raw resistivity and magnetization curves, and provide XRD and EDS characterization confirming the composition and phase purity of the x = 0.4 specimen. revision: yes

  2. Referee: [Results / Discussion] Results section: The manuscript notes that Tc in the parent compound varies from 1.2 to 1.6 K due to non-stoichiometry but provides no comparative synthesis controls, phase-purity data, or multiple-batch measurements for the x = 0.4 specimen to isolate the effect of the intentional Na1+xSn2-x substitution.

    Authors: The variation in the parent compound is cited to illustrate sensitivity to stoichiometry. To strengthen isolation of the doping effect we will include additional phase-purity data and, where available, results from multiple synthesis batches of the x = 0.4 material in the revised version. revision: yes

  3. Referee: [Computational Methods / Results] DFT section: While the calculations indicate NaSn antisites are lower in energy than vacancies, there is no analysis of the solubility limit at x = 0.4 or of possible phase separation, which is required to link the defect energetics to the observed Tc enhancement.

    Authors: The DFT results are presented to establish that NaSn antisites are the lowest-energy cation defect, thereby supporting the feasibility of the proposed substitution. A quantitative solubility-limit or phase-separation analysis at x = 0.4 would require additional supercell and finite-temperature modeling that lies outside the scope of the present study. We will add a short clarifying paragraph noting the qualitative nature of the computational support. revision: partial

Circularity Check

0 steps flagged

No circularity: experimental Tc values and separate DFT defect energies are independent.

full rationale

The paper reports measured superconducting transition temperatures (Tc = 1.2–1.6 K baseline, 2.1 K at x = 0.4) from sample synthesis and transport measurements, together with first-principles total-energy calculations showing Na_Sn antisite defects are favored. No equations, fitted parameters, or self-citations are presented that reduce the reported Tc enhancement to a quantity defined by the same data. The two strands of evidence remain distinct and externally falsifiable.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Paper rests on standard DFT defect-energy calculations and the assumption that measured Tc differences arise from the stated doping; no free parameters or invented entities are introduced in the abstract.

axioms (1)
  • domain assumption First-principles calculations reliably rank the formation energies of cation defects in Na-Sn-As layered compounds.
    Invoked to conclude NaSn antisite defects are favored over other vacancies.

pith-pipeline@v0.9.0 · 5704 in / 1118 out tokens · 39922 ms · 2026-05-24T18:01:18.570262+00:00 · methodology

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Reference graph

Works this paper leans on

31 extracted references · 31 canonical work pages · 1 internal anchor

  1. [1]

    Y . Goto, A. Yamada, T. D. Matsuda, Y . Aoki, and Y . Mizuguchi, J. Phys. Soc. Jpn. 86, 123701 (2017)

    work page 2017

  2. [2]

    Ishihara, T

    K. Ishihara, T. Takenaka, Y . Miao, O. Tanaka, Y . Mizukami, H. Usui, K. Kuroki, M. Konczykowski, Y . Goto, Y . Mizuguchi, and T. Shibauchi, Phys. Rev. B 98, 20503 (2018)

    work page 2018

  3. [3]

    E. J. Cheng, J. M. Ni, F. Q. Meng, T. P. Ying, B. L. Pan, Y . Y . Huang, Darren Peets, Q. H. Zhang, S. Y . Li, EPL 123, 47004 (2018)

    work page 2018

  4. [4]

    K. Lee, D. Kaseman, S. Sen, I. Hung, Z. Gan, B. Gerke, R. Po, M. Feygenson, J. Neuefeind, O. I. Lebedev, and K. Kovnir, J. Am. Chem. Soc. 137, 3622 (2015)

    work page 2015

  5. [5]

    Z. Lin, G. Wang, C. Le, H. Zhao, N. Liu, J. Hu, L. Guo, and X. Chen, Phys. Rev. B 95, 165201 (2017)

    work page 2017

  6. [6]

    Q. D. Gibson, L. M. Schoop, L. Muechler, L. S. Xie, M. Hirschberger, N. P. Ong, R. Car, and R. J. Cava, Phys. Rev. B 91, 205128 (2015)

    work page 2015

  7. [7]

    L. Y . Rong, J. Z. Ma, S. M. Nie, Z. P. Lin, Z. L. Li, B. . B. Fu, L. Y . Kong, Z. Z. Zhang, Y . B. Huang, H. M. Weng, T. Qian, H. Ding, and R. Z. Tai, Sci. Rep. 7, 6133 (2017)

    work page 2017

  8. [8]

    B. He, Y . Wang, M. Q. Arguilla, N. D. Cultrara, M. R. Scudder, J. E. Goldberger, W. Windl, and J. P. Heremans, Nat. Mater. DOI: 10.1038/s41563-019-0309-4 (2019)

    work page doi:10.1038/s41563-019-0309-4 2019

  9. [9]

    X. Gui, I. Pletikosic, H. Cao, H. Tien, X. Xu, R. Zhong, G. Wang, T.-R. Chang, S. Jia, T. Valla, W. Xie, and R. J. Cava, arXiv:1903.03888 (2019)

    work page internal anchor Pith review Pith/arXiv arXiv 1903

  10. [10]

    T. E. Weller, M. Ellerby, S. S. Saxena, R. P. Smith, and N. T. Skipper, Nat. Phys. 1, 39 (2005)

    work page 2005

  11. [11]

    Yamanaka, K

    S. Yamanaka, K. Hotehama, and H. Kawaji, Nature (London) 392, 580 (1998)

    work page 1998

  12. [12]

    D. Kang, Y . Zhou, W. Yi, C. Yang, J. Guo, Y . Shi, S. Zhang, Z. Wang, C. Zhang, S. Jiang, A. Li, K. Yang, Q. Wu, G. Zhang, L. Sun, and Z. Zhao, Nat. Commun. 6, 7804 (2015)

    work page 2015

  13. [13]

    X.-C. Pan, X. Chen, H. Liu, Y . Feng, Z. Wei, Y . Zhou, Z. Chi, L. Pi, F. Yen, F. Song, X. Wan, Z. Yang, B. Wang, G. Wang, and Y . Zhang, Nat. Commun. 6, 7805 (2015)

    work page 2015

  14. [14]

    Y . Qi, P. G. Naumov, M. N. Ali, C. R. Rajamathi, W. Schnelle, O.Barkalov, M. Hanfland, S.-C. Wu, C. Shekhar, Y . Sun, V . Süß, M. Schmidt, U. Schwarz, E. Pippel, P. Werner, R. Hillebrand, T. Förster, E. Kampert, S. Parkin, R. J. Cava et al., Nat. Commun. 7, 11038 (2016). Template for JJAP Regular Papers (Jan. 2014) 9

    work page 2016

  15. [15]

    Taniguchi, A

    K. Taniguchi, A. Matsumoto, H. Shimotani, and H. Takagi, Appl. Phys. Lett. 101, 042603 (2012)

    work page 2012

  16. [16]

    M. Q. Arguilla, J. Katoch, K. Krymowski, N. D. Cultrara, J. Xu, X. Xi, A. Hanks, S. Jiang, R. D. Ross, R. J. Koch, S. Ulstrup, A. Bostwick, C. Jozwiak, D. W. Mccomb, E. Rotenberg, J. Shan, W. Windl, R. K. Kawakami, and J. E. Goldberger, ACS Nano 10, 9500 (2016)

    work page 2016

  17. [17]

    M. Q. Arguilla, N. D. Cultrara, Z. J. Baum, S. Jiang, R. D. Ross, and J. E. Goldberger, Inorg. Chem. Front. 2, 378 (2017)

    work page 2017

  18. [18]

    Y . Goto, A. Miura, C. Moriyoshi, Y . Kuroiwa, T. D. Matsuda, Y . Aoki, and Y . Mizuguchi, Sci. Rep. 8, 12852 (2018)

    work page 2018

  19. [19]

    S. B. Zhang, S. -H. Wei, and A. Zunger, and H. Katayama -Yoshida, Phys. Rev. B 57, 9642 (1998)

    work page 1998

  20. [20]

    Kawaguchi, M

    S. Kawaguchi, M. Takemoto, K. Osaka, E. Nishibori, C. Moriyoshi, Y . Ku bota, Y . Kuroiwa, K. Sugimoto, Rev. Sci. Instrum. 88, 85111 (2017)

    work page 2017

  21. [21]

    Izumi and K

    F. Izumi and K. Momma, Solid State Phenom. 130, 15 (2007)

    work page 2007

  22. [22]

    Momma and F

    K. Momma and F. Izumi, J. Appl. Crystallogr. 41, 653 (2008)

    work page 2008

  23. [23]

    Kresse and J

    G. Kresse and J. Furthmüller, Comput. Mater. Sci. 6, 15 (1996)

    work page 1996

  24. [24]

    Kresse and J

    G. Kresse and J. Furthmüller, Phys. Rev. B 54, 11169 (1996)

    work page 1996

  25. [25]

    J. P. Perdew, K. Burke, and M. Emzerhof, Phys. Rev. Lett. 77, 3865 (1996)

    work page 1996

  26. [26]

    Pugliese, F

    G. Pugliese, F. Stramaglia, Y . Goto, K. Terashima, L. Simonelli, H. Fujiwara, A. Puri, C. Marini, F. D’Acapito, T. Yokoya, T. Mizokawa, Y . Mizuguchi, and N. L. Saini, J. Phys: Cond. Mat. (in press)

    work page

  27. [27]

    N. R. Werthamer, E. Helfand, and P. C. Hohemberg, Phys. Rev. 147, 295 (1966)

    work page 1966

  28. [28]

    Y . Wang, H. Sato, Y . Toda, S. Ueda, H. Hiramatsu, and H. Hosono, Chem. Mater. 26, 7209 (2014)

    work page 2014

  29. [29]

    S. Chen, J. -H. Yang, X. G. Gong, A. Walsh, and S. -H. Wei, Phys. Rev. B 81, 245204 (2010)

    work page 2010

  30. [30]

    Zakutayev, J

    A. Zakutayev, J. Tate, and G. Schneider, Phys. Rev. B 82, 195204 (2010)

    work page 2010

  31. [31]

    D. O. Scanlon, J. Buckeridge, C. Richard, A. Catlow, and G. W. Watson, J. Mater. Chem. C 2, 3429 (2014). Template for JJAP Regular Papers (Jan. 2014) 10 Figure Captions Fig. 1. Crystallographic structure of Na1+xSn2xAs2 (x = 0.3). Na and Sn sites show slightly mixed occupation (see text for details). Fig. 2. (a) Powder X-ray diffraction (PXRD) patterns f...

    work page 2014