arxiv: 2604.09172 · v1 · submitted 2026-04-10 · ❄️ cond-mat.supr-con

Nonmonotonic Evolution of the Superconducting Transition Temperature and Robust Multigap Extended s-wave + s-wave Pairing in Zn-Substituted FeSe Single Crystals

Han-Shu Xu , Changhao Ding , Guanyin Gao , Xin Zhang , Xinyu Yin , Xucai Kan , Jiaping Hu , Wen Xie

show 6 more authors

Wensen Wei Yuxiao Hou Keyu An Haoxiang Li Kaibin Tang Yu-Yan Han

This is my paper

Pith reviewed 2026-05-10 16:46 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con

keywords FeSezinc substitutionmultigap superconductivityextended s-wave pairingspecific heat analysisnonmonotonic Tcpairing symmetry

0 comments

The pith

Zinc substitution in FeSe leads to nonmonotonic superconducting transition temperature while preserving robust multigap s-wave plus extended s-wave pairing.

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

The study investigates the effects of zinc doping on the superconductivity in iron selenide single crystals across a range of concentrations. The transition temperature displays a nonmonotonic evolution with zinc content, pointing to mechanisms beyond simple impurity pair breaking. Low temperature specific heat measurements are well fit by a model involving two superconducting gaps, one isotropic s-wave and one anisotropic extended s-wave, while other models do not fit. The relative contributions of these gaps stay similar with doping, implying weak interband scattering and the stability of the multigap state. This robustness constrains possible pairing theories for iron-based superconductors by emphasizing the role of their multiband structure.

Core claim

We report that in Fe1-xZnxSe single crystals for x from 0 to 0.023, the superconducting transition temperature Tc varies nonmonotonically with x, and that the low-temperature specific heat is consistently described by a two-gap scenario with an isotropic s-wave gap and an anisotropic extended s-wave gap. Single-gap and alternative pairing symmetries fail to describe the data, and the nearly unchanged relative weights of the two gap components indicate weak interband scattering induced by Zn substitution, thereby preserving multigap superconductivity in FeSe.

What carries the argument

The two-gap model consisting of an isotropic s-wave gap and an anisotropic extended s-wave gap, fitted to specific heat data to demonstrate the persistence of multigap pairing under Zn doping.

If this is right

The nonmonotonic dependence of Tc on Zn concentration suggests that the evolution of superconductivity involves more than impurity pair breaking effects.
Multigap superconductivity remains robust, with weak interband scattering preserving the two-gap structure.
The findings impose constraints on candidate pairing mechanisms, highlighting the importance of multiband electronic structure and anisotropic gap formation.
Enhanced scattering effects with Zn doping are observed in magnetization and transport measurements, yet bulk superconductivity persists.

Where Pith is reading between the lines

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

Similar doping experiments in other multiband superconductors could test if this robustness of multigap pairing is widespread.
The anisotropic nature of one gap may be linked to the specific Fermi surface topology in FeSe.
Doping-dependent changes in Tc could arise from a balance between carrier doping and scattering rates.

Load-bearing premise

The low-temperature specific heat can be uniquely attributed to the two-gap isotropic s-wave plus anisotropic extended s-wave pairing without significant contributions from sample inhomogeneity, vortex effects, or other unmodeled scattering.

What would settle it

Observation of specific heat behavior better fit by a single gap or alternative symmetry like d-wave pairing in similar Zn-substituted FeSe samples would falsify the two-gap model.

read the original abstract

We report a systematic study of superconductivity on Fe1-xZnxSe single crystals synthesized over a broad Zn doping range (x = 0-0.023). High-quality single crystals across all compositions range exhibit superconducting transitions, while the transition temperature Tc shows a pronounced nonmonotonic dependence on Zn doping concentration, indicating that the underlying mechanism govering Tc its evolution cannot be explained solely by simple impurity pair breaking alone. Magnetization and transport measurements confirm the bulk behavior of superconductivity and reveal enhanced scattering effects with Zn doping. Low-temperature specific heat is consistently described by a two-gap scenario composed of an isotropic s-wave gap and an anisotropic extended s-wave gap, whereas single-gap and alternative pairing symmetries fail to describe the data. The nearly unchanged relative weights of the two gap components suggest the weak interband scattering induced by Zn substitution, thereby preserving multiband superconductivity. These results demonstrate the robustness of multigap superconductivity in FeSe and impose stringent constraints on candidate pairing mechanisms, highlighting the role of multiband electronic structure and anisotropic gap formation.

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.

Desk Editor's Note private letter to a colleague

Zn doping in FeSe produces nonmonotonic Tc while the specific-heat data still require the same two-gap fit with stable weights, though the uniqueness of that attribution is not fully secured.

read the letter

Zn substitution in FeSe single crystals produces a nonmonotonic Tc versus doping curve while the low-temperature specific heat continues to fit an isotropic s-wave plus anisotropic extended s-wave two-gap model, with the relative weights of the two components staying nearly constant across the series up to x=0.023. Magnetization and transport data confirm bulk superconductivity throughout the doping window. The nonmonotonic Tc is the clearest new observation; it cannot be explained by simple pair-breaking and therefore adds a concrete constraint on how Zn affects the underlying pairing in this material. The persistence of the two-gap structure with little change in weights is also useful, as it suggests the substitution induces only weak interband scattering. The experimental series itself is straightforward and well-executed on the growth and basic characterization side. The soft spot is the specific-heat modeling. The paper states that single-gap and alternative symmetries fail while the two-gap scenario succeeds, but the abstract gives no quantitative fit statistics, error bars on the parameters, or explicit checks against inhomogeneity broadening or vortex contributions. Those effects can produce apparent multi-gap signatures in C(T), so the claim that the data uniquely select isotropic s plus extended s needs the full fitting details and any field-dependent measurements to hold up. This work is mainly for the iron-chalcogenide community that tracks multigap phenomenology in FeSe. A reader already familiar with the undoped material will find the doping dependence and weight stability worth noting. It deserves peer review because the core measurements are standard and the nonmonotonic Tc result is testable, even if the gap-fitting section will likely need tightening.

Referee Report

1 major / 3 minor

Summary. The manuscript reports a systematic investigation of Zn-substituted FeSe single crystals (x = 0–0.023). It observes a nonmonotonic dependence of Tc on Zn concentration that cannot be attributed solely to impurity pair breaking, confirms bulk superconductivity via magnetization and transport, and analyzes low-temperature specific-heat data. The central claim is that these data are consistently described by a two-gap model (isotropic s-wave gap plus anisotropic extended s-wave gap) while single-gap and other symmetry alternatives fail; the stable relative weights of the two gaps are interpreted as evidence for weak interband scattering, implying robust multigap superconductivity in FeSe that constrains pairing mechanisms.

Significance. If the two-gap attribution of the specific-heat data holds after additional checks, the work would be significant for iron-based superconductivity by demonstrating the persistence of multigap pairing under non-magnetic substitution and by supplying concrete experimental constraints on candidate gap symmetries and interband scattering strengths in FeSe.

major comments (1)

Specific-heat analysis (Results/Discussion section): The claim that low-T specific heat is 'consistently described by a two-gap scenario' while single-gap and alternative symmetries fail is load-bearing for the central conclusion and the interpretation of weak interband scattering. However, the manuscript provides no quantitative fitting details (e.g., explicit values or ranges for the isotropic gap amplitude, the extended-s amplitude and anisotropy parameter, or the relative spectral weight), no goodness-of-fit metrics, and no explicit exclusion of inhomogeneity or vortex contributions. This leaves the uniqueness of the model unverified against the possibility that transition broadening or unmodeled scattering could mimic the reported two-gap signature.

minor comments (3)

Abstract: The phrase 'mechanism govering Tc its evolution' contains a typographical error and grammatical issue; it should read 'mechanism governing the evolution of Tc'.
Abstract and main text: The statement that 'single-gap and alternative pairing symmetries fail to describe the data' would benefit from a brief reference to the specific functional forms or comparison plots used, even if details appear in a later section.
The manuscript could clarify how the 'enhanced scattering effects with Zn doping' are quantified from the transport data (e.g., residual resistivity ratio or scattering rate estimates) to support the claim of weak interband scattering.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the constructive feedback. The positive assessment of the overall significance is appreciated. We address the single major comment point by point below and will revise the manuscript to strengthen the specific-heat analysis as requested.

read point-by-point responses

Referee: Specific-heat analysis (Results/Discussion section): The claim that low-T specific heat is 'consistently described by a two-gap scenario' while single-gap and alternative symmetries fail is load-bearing for the central conclusion and the interpretation of weak interband scattering. However, the manuscript provides no quantitative fitting details (e.g., explicit values or ranges for the isotropic gap amplitude, the extended-s amplitude and anisotropy parameter, or the relative spectral weight), no goodness-of-fit metrics, and no explicit exclusion of inhomogeneity or vortex contributions. This leaves the uniqueness of the model unverified against the possibility that transition broadening or unmodeled scattering could mimic the reported two-gap signature.

Authors: We agree that additional quantitative details are needed to fully substantiate the two-gap model and its uniqueness. In the revised manuscript we will add explicit fitting parameters for the isotropic s-wave gap amplitude, the extended s-wave gap amplitude together with its anisotropy parameter, and the relative spectral weights of the two components. We will also report goodness-of-fit metrics (reduced chi-squared values) comparing the two-gap model against single-gap and alternative symmetry scenarios to demonstrate the statistically superior description. On inhomogeneity, the sharp transitions in both resistivity and magnetization, combined with near-100% shielding fractions, already indicate homogeneous bulk superconductivity; we will explicitly state this and add a brief discussion ruling out significant broadening effects. For vortex contributions, all specific-heat measurements were performed in zero field after zero-field cooling, rendering vortex-related terms negligible; this will be clarified in the revised text. These additions will confirm that the two-gap signature cannot be mimicked by the suggested alternatives and will reinforce the conclusion of weak interband scattering. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental fitting of specific-heat data to standard multigap models

full rationale

The paper's core claims rest on direct synthesis, magnetization, transport, and low-T specific-heat measurements across Zn-doped FeSe crystals, followed by standard model fitting to distinguish single-gap vs. two-gap (isotropic s + anisotropic extended-s) scenarios. No load-bearing self-citations, no self-definitional equations, no fitted parameters renamed as predictions, and no uniqueness theorems imported from the authors' prior work. Gap functional forms are conventional in the multiband superconductivity literature and are tested against the data rather than derived from the present results. The derivation chain is therefore self-contained against external experimental benchmarks.

Axiom & Free-Parameter Ledger

3 free parameters · 2 axioms · 0 invented entities

This is an experimental condensed-matter study whose claims rest on standard assumptions of BCS-like gap fitting and on parameters extracted from specific-heat data; no new particles or forces are postulated.

free parameters (3)

isotropic s-wave gap amplitude
Fitted to low-T specific heat; value not stated in abstract but required for the two-gap model.
anisotropic extended s-wave gap amplitude and anisotropy parameter
Fitted to low-T specific heat; value not stated in abstract but required for the two-gap model.
relative spectral weight of the two gaps
Fitted or extracted from specific-heat data; reported as nearly constant with doping.

axioms (2)

domain assumption Specific heat at low T is dominated by quasiparticle excitations across the superconducting gaps with negligible phonon or impurity contributions after standard subtraction.
Invoked when claiming that the two-gap model uniquely describes the data.
domain assumption The functional forms chosen for the isotropic s-wave and anisotropic extended s-wave gaps are appropriate for the Fermi-surface sheets in FeSe.
Required to interpret the fit as evidence for extended s-wave pairing.

pith-pipeline@v0.9.0 · 5549 in / 1619 out tokens · 57960 ms · 2026-05-10T16:46:56.859427+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

57 extracted references · 57 canonical work pages

[1]

Introduction Since its discovery, FeSe has attracted extensive attention due to its unique properties. On the one hand, FeSe possesses a relatively simple crystal structure (space group P4/nmm), making it an ideal platform for investigating the intrinsic physics of iron -based superconductors [1,2]. On the other hand, its Tc is highly sensitive to externa...

work page
[2]

Subsequently, 6.22 g AlCl3 (99.9%, Aladdin) and 1.73 g KCl (99.99%, Aladdin) were added as fluxes to facilitate mass transport and the kinetics of crystal growth

Experimental section and Characterization In the crystal growth process of FeSe single crystals, 0.62 g of reduced iron powder (99.99%, Alfa Aesar) and 0.78 g of selenium grains (99.999%, Alfa Aesar) were first weighed and loaded into a quartz tube with an outer diameter of 15 mm and a wall thickness of 1.5 mm. Subsequently, 6.22 g AlCl3 (99.9%, Aladdin) ...

work page
[3]

1 Phase diagram of Zn -substituted FeSe single crystals, Fe1-xZnxSe, as a function of Zn concentration x

Experimental Results and Discussions Fig. 1 Phase diagram of Zn -substituted FeSe single crystals, Fe1-xZnxSe, as a function of Zn concentration x. The Tc are determined from magnetization (M), resistivity (ρ), and specific heat (C) measurements. To verify the crystallinity of Fe1-xZnxSe single crystals with different Zn contents, XRD measurements were pe...

work page
[4]

Hsu, J.-Y

F.-C. Hsu, J.-Y . Luo, K.-W. Yeh, T.-K. Chen, T.-W. Huang, P . M. Wu, Y.-C. Lee, Y.-L. Huang, Y.-Y . Chu, D.-C. Yan, and M.-K. Wu, Proc. Natl. Acad. Sci. U. S. A. 105, 14262-14264 (2008)

work page 2008
[5]

Q. Fan, W. H. Zhang, X. Liu, Y . J. Yan, M. Q. Ren, R. Peng, H. C. Xu, B. P. Xie, J. P. Hu, T. Zhang, and D. L. Feng, Nat. Phys. 11, 946-952 (2015)

work page 2015
[6]

Burrard-Lucas, D

M. Burrard-Lucas, D. G. Free, S. J. Sedlmaier, J. D. Wright, S. J. Cassidy, Y . Hara, A. J. Corkett, T. Lancaster, P. J. Baker, and S. J. Blundell, Nat. Mater. 12, 15-19 (2013)

work page 2013
[7]

M. Z. Shi, N. Z. Wang, B. Lei, C. Shang, F. B. Meng, L. K. Ma, F. X. Zhang, D. Z. Kuang, and X. H. Chen, Phys. Rev. Mater. 2, 074801 (2018)

work page 2018
[8]

Z. Gao, S. Y . Zeng, B. C. Zhu, B. Li, Q. Y . Hao, Y . W. Hu, D. K. Wang, and K. B. Tang, Sci. China Mater. 61, 977-984 (2018)

work page 2018
[9]

S. S. Sun, S. H. Wang, R. Yu, and H. C. Lei, Phys. Rev. B 96, 064512 (2017)

work page 2017
[10]

Kothapalli, A

K. Kothapalli, A. E. Böhmer, W. T. Jayasekara, B. G. Ueland, P. Das, A. Sapkota, V . Taufour, Y . Xiao, E. Alp, S. L. Bud’ko, P. C. Canfield, A. Kreyssig, and A. I. Goldman, Nat. Commun. 7, 12728 (2016)

work page 2016
[11]

P. S. Wang, S. S. Sun, Y . Cui, W. H. Song, T. R. Li, R. Yu, H. C. Lei, W. Q. Yu, Phys. Rev. Lett. 117, 237001 (2016)

work page 2016
[12]

J. P. Sun, K. Matsuura, G. Z. Ye, Y . Mizukami, M. Shimozawa, K. Matsubayashi, M. Yamashita, T. Watashige, S. Kasahara, Y . Matsuda, J. Q. Yan, B. C. Sales, Y . Uwatoko, J. G. Cheng, and T. Shibauchi, Nat. Commun. 7, 12146 (2016)

work page 2016
[13]

J. Y . Lin, Y . S. Hsieh, D. A. Chareev, A. N. Vasiliev, Y . Parsons, and H. D. Yang, Phys. Rev. B 84, 220507(R) (2011)

work page 2011
[14]

A. V . Muratov, A.V . Sadakov, S. Y . Gavrilkin, A. R. Prishchepa, G. S. Epifanova, D. A. Chareev, and V . M. Pudalov, Phys. B (Amsterdam, Neth.) 536, 785-789 (2018)

work page 2018
[15]

J. T. Chen, Y . Sun, T. Yamada, S. Pyon, and T. Tamegai, J. Phys.:Conf. Ser. 871, 012016 (2017)

work page 2017
[16]

G.-Y . Chen, X. Y . Zhu, H. Yang, and H.-H. Wen, Phys. Rev. B 96, 064524 (2017)

work page 2017
[17]

Bourgeois-Hope, S

P. Bourgeois-Hope, S. Chi, D. A. Bonn, R. Liang, W. N. Hardy, T. Wolf, C. Meingast, N. Doiron-Leyraud, and L. Taillefer, Phys. Rev. Lett. 117, 097003 (2016)

work page 2016
[18]

J. K. Dong, T. Y . Guan, S. Y . Zhou, X. Qiu, L. Ding, C. Zhang, U. Patel, Z. L. Xiao, and S. Y . Li, Phys. Rev. B 80, 024518 (2009)

work page 2009
[19]

Watashige, S

T. Watashige, S. Arsenijević, T. Yamashita, D. Terazawa, T. Onishi, L. Opherden, S. Kasahara, Y . Tokiwa, Y . Kasahara, T. Shibauchi, H. v. Löhneysen, J. Wosnitza, and Y . Matsuda, J. Phys. Soc. Jpn. 86, 014707 (2017)

work page 2017
[20]

Song, Y .-L

C.-L. Song, Y .-L. Wang, P. Cheng, Y .-P. Jiang, W. Li, T. Zhang, Z. Li, K. He, L. Wang, J.-F. Jia, H.-H. Hung, C. Wu, X. Ma, X. Chen, and Q.-K. Xue, Science 332, 1410-1413 (2011)

work page 2011
[21]

L. Jiao, S. Rößler, C. Koz, U. Schwarz, D. Kasinathan, U. K. Rößler, and S. Wirth, Phys. Rev. B 96, 094504 (2017)

work page 2017
[22]

S. N. Rebec, T. Jia, C. Zhang, M. Hashimoto, D. H. Lu, R. G. Moore, and Z. X. Shen, Phys. Rev. Lett. 118, 067002 (2017)

work page 2017
[23]

P. W. Anderson, J. Phys. Chem. Solids 11, 26 (1959)

work page 1959
[24]

A. V . Balatsky, I. Vekhter, J.-X. Zhu, Rev. Mod. Phys. 78, 373 (2006)

work page 2006
[25]

I. I. Mazin, D. J. Singh, M. D. Johannes, and M. H. Du, Phys. Rev. Lett. 101, 057003 (2008)

work page 2008
[26]

Xu, Y .-J

H.-S. Xu, Y .-J. Yan, R. T. Yin, W. Xia, S. J. Fang, Z. Y . Chen, Y . J. Li, W. Q. Yang, Y . F. Guo, and D.-L. Feng, Phys. Rev. Lett. 127, 187004 (2021)

work page 2021
[27]

A. A. Abrikosov and L. P. Gorkov, Sov. Phys. JETP 12, 337 (1961)

work page 1961
[28]

D. Wang, L. Kong, P. Fan, H. Chen, S. Zhu, W. Liu, L. Cao, Y . Sun, S. Du, J. Schneeloch, R. Zhong, G. Gu, L. Fu, H. Ding, and H.-J. Gao, Science 362, 333 (2018)

work page 2018
[29]

A. J. Williams, T. M. McQueen, R. J. Cava, V . Ksenofontov, and C. Felser, J. Phys. Condens. Matter 21, 305701 (2009)

work page 2009
[30]

H. Li, M. Ma, S. Liu, F. Zhou, and X. Dong, Chin. Phys. B 29, 127404 (2020)

work page 2020
[31]

C. S. Gong, S. S. Sun, S. H. Wang, and H. C. Lei, Phys. Rev. B 103, 174510 (2021)

work page 2021
[32]

Urata, Y

T. Urata, Y . Tanabe, K. K. Huynh, Y . Yamakawa, H. Kontani, and K. Tanigaki, Phys. Rev. B 93, 014507 (2016)

work page 2016
[33]

Perez, J

I. Perez, J. A. McLeod, R. J. Green, R. Escamilla, V . Ortiz, and A. Moewes, Phys. Rev. B 90, 014510 (2014)

work page 2014
[34]

Yousuf, J

S. Yousuf, J. Song, H. Jang, V. T. A. Hong, T. Lee, N. u. Ain, Shin Y . H, Y. Kim, H. Lee, and T. Park, Curr . Appl. Phys. 61, 7-11 (2024)

work page 2024
[35]

Pokharel, C

G. Pokharel, C. X. Zhang, E. Redekop, B. R. Ortiz, A. N. C. Salinas, S. Schwarz, S. J. G. Alvarado, S. Sarker, A. F. Young, and S. D. Wilson, Phys. Rev. Mater. 9, 094805 (2025)

work page 2025
[36]

Shtefiienko, T

K. Shtefiienko, T. Beekmann, M. J. Stitz, G. Pokharel, S. D. Wilson, C. A. Mizzi, D. E. Graf, and K. Shrestha, Phys. Rev. B 113, 035119 (2026)

work page 2026
[37]

Tinkham, Introduction to Superconductivity, 2nd ed

M. Tinkham, Introduction to Superconductivity, 2nd ed. (McGraw-Hill, New York, 1996)

work page 1996
[38]

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

work page 1966
[39]

W. S. Wei, G. J. Zhao, D. R. Kim, C. M. Jin, J. L. Zhang, L. S. Ling, L. Zhang, H. F. Du, T. Y . Chen, J. D. Zang, M. L. Tian, C. L. Chien, and Y . H. Zhang, Phys. Rev. B 94, 104503 (2016)

work page 2016
[40]

K. K. Huynh, Y . Tanabe, T. Urata, H. Oguro, S. Heguri, K. Watanabe, and K. Tanigaki, Phys. Rev. B 90, 144516 (2014)

work page 2014
[41]

Kasahara, T

S. Kasahara, T. Watashige, T. Hanaguri, Y. Kohsaka, T. Yamashita, Y. Shimoyama, Y. Mizukami, R. Endo, H. Ikeda, K. Aoyama, T. Terashima, S. Uji, T. Wolf, H. v. Löhneysen, T. Shibauchi, and Y. Matsuda, Proc. Natl. Acad. Sci. U. S. A. 111, 16309-16313 (2014)

work page 2014
[42]

A. B. Pippard, Magnetoresistance in Metals, V ol. 2 (Cambridge University Press, Cambridge, UK, 1989)

work page 1989
[43]

Terashima, N

T. Terashima, N. Kikugawa, A. Kiswandhi, E.-S. Choi, J. S. Brooks, S. Kasahara, T. Watashige, H. Ikeda, T. Shibauchi, Y. Matsuda, T. Wolf, A. E. Böhmer, F. Hardy, C. Meingast, H. v. Löhneysen, M.-T. Suzuki, R. Arita, and S. Uji, Phys. Rev. B 90, 144517 (2014)

work page 2014
[44]

N. W. Ashcroft and N. D. Mermin, Solid State Physics (Holt, Rinehart and Winston, New York, 1976)

work page 1976
[45]

M. D. Watson, T. K. Kim, A. A. Haghighirad, N. R. Davies, A. McCollam, A. Narayanan, S. F. Blake, Y . L. Chen, S. Ghannadzadeh, A. J. Schofield, M. Hoesch, C. Meingast, T. Wolf, and A. I. Coldea, Phys. Rev. B 91, 155106 (2015)

work page 2015
[46]

A. Tari. in Specific Heat of Matter at Low Temperatures (Imperial College Press, London, 2003)

work page 2003
[47]

Padamsee, J

H. Padamsee, J. E. Neighbor, and C. A. Shiffman, J. Low Temp. Phys. 12, 387 (1973)

work page 1973
[48]

Mühlschlegel, Z

B. Mühlschlegel, Z. Phys. 155, 313 (1959)

work page 1959
[49]

C. C. Tsuei and J. R. Kirtley, Rev. Mod. Phys. 72, 969 (2000)

work page 2000
[50]

Kuroki, S

K. Kuroki, S. Onari, R. Arita, H. Usui, Y. Tanaka, H. Kontani, and H. Aoki, Phys. Rev. Lett. 101, 087004 (2008)

work page 2008
[51]

Sigrist and K

M. Sigrist and K. Ueda, Rev. Mod. Phys. 63, 239 (1991)

work page 1991
[52]

S. N. Rebec, T. Jia, C. Zhang, M. Hashimoto, D. -H. Lu, R. G. Moore, and Z. -X. Shen, Phys. Rev. Lett. 118, 067002 (2017)

work page 2017
[53]

Bouquet, Y

F. Bouquet, Y . Wang, R. A. Fisher, D. G. Hinks, J. D. Jorgensen, A. Junod, and N. E. Phillips, Europhys. Lett. 56, 856 (2001)

work page 2001
[54]

Carrington and F

A. Carrington and F. Manzano, Phys. C (Amsterdam, Neth.) 385, 205-214 (2003)

work page 2003
[55]

Kontani and S

H. Kontani and S. Onari, Phys. Rev. Lett. 104, 157001 (2010)

work page 2010
[56]

D. V . Efremov, M. M. Korshunov, O. V . Dolgov, A. A. Golubov, and P. J. Hirschfeld, Phys. Rev. B 84, 180512 (2011)

work page 2011
[57]

Yao, W.-Q

Z.-J. Yao, W.-Q. Chen, Y.-k. Li, G.-h. Cao, H.-M. Jiang, Q.-E. Wang, Z.-a. Xu, and F.-C. Zhang, Phys. Rev. B 86, 184515 (2012)

work page 2012