Recognition: 2 theorem links
· Lean TheoremEuler Topology in Superconducting Honeycomb Lattices
Pith reviewed 2026-05-13 01:37 UTC · model grok-4.3
The pith
Superconducting pairings on honeycomb lattices give rise to Euler superconductors with protected helical modes.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
In IST-symmetric superconducting honeycomb lattices, s-wave spin-singlet (SWSS) pairings give rise to valley-Euler superconductors and f-wave spin-triplet (FWST) pairings give rise to Euler superconductors. The Euler topology in both pairing states leads to mirror-symmetry-protected helical domain-wall modes. In the FWST state, this topology induces non-Abelian braiding of Dirac nodes in momentum space when anisotropic hopping is introduced. Superconducting electronic instabilities thus provide a natural route to realizing nontrivial Euler band topology in Dirac materials.
What carries the argument
The Euler topology of the bands enabled by space-time inversion symmetry, which classifies the superconducting states and enforces helical domain-wall modes plus Dirac-node braiding.
If this is right
- Mirror symmetry protects helical domain-wall modes in both the valley-Euler and Euler superconducting states.
- Anisotropic hopping in the f-wave spin-triplet state induces non-Abelian braiding of Dirac nodes.
- Superconducting instabilities offer a route to Euler topology in systems with Dirac bands.
- The distinction between valley-Euler and full Euler superconductivity arises from the choice of pairing symmetry.
Where Pith is reading between the lines
- The same pairing-induced mechanism could appear in other two-dimensional Dirac lattices that preserve space-time inversion symmetry.
- Anisotropy provides an experimental tuning parameter to control the braiding of Dirac nodes in fabricated samples.
- The helical modes could be probed through local spectroscopy or transport at engineered domain walls in real materials.
Load-bearing premise
The superconducting honeycomb lattices must possess space-time inversion symmetry for their bands to host nontrivial Euler topology.
What would settle it
Numerical or experimental absence of mirror-protected helical modes at domain walls, or a zero Euler invariant in the calculated band structure for the predicted pairings, would disprove the claims.
Figures
read the original abstract
Electronic bands in systems with space-time inversion (IST) symmetry can host nontrivial Euler topology. Here, we investigate the band topology of IST-symmetric superconducting honeycomb lattices and demonstrate that s-wave spin-singlet (SWSS) and f-wave spin-triplet (FWST) superconducting pairings give rise to valley-Euler and Euler superconductors, respectively. We find that Euler topology in both pairing states gives rise to mirror-symmetry-protected helical domain-wall modes. Furthermore, we show that Euler topology in the FWST state induces non-Abelian braiding of Dirac nodes in momentum space when anisotropic hopping is introduced. Our work establishes superconducting electronic instabilities as a natural route to realizing nontrivial Euler band topology in Dirac materials.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims that IST-symmetric superconducting honeycomb lattices with s-wave spin-singlet (SWSS) pairing realize valley-Euler superconductors while f-wave spin-triplet (FWST) pairing realizes Euler superconductors. Euler topology in both cases produces mirror-symmetry-protected helical domain-wall modes, and anisotropic hopping in the FWST state further induces non-Abelian braiding of Dirac nodes in momentum space. The work positions superconducting instabilities as a route to nontrivial Euler topology in Dirac materials.
Significance. If the IST symmetry is preserved by the chosen pairings and the Euler class is correctly computed, the results would identify a concrete mechanism for realizing Euler topology and its protected modes in superconductors, with potential relevance to helical edge states and non-Abelian statistics. The approach relies on standard symmetry classification rather than ad-hoc parameters.
major comments (2)
- [Abstract and BdG Hamiltonian section] The central claims require that both the SWSS and FWST order parameters preserve IST symmetry in the BdG Hamiltonian so that the bands remain real and admit a well-defined Euler class. The abstract asserts IST symmetry of the lattices but supplies no explicit commutation relation, matrix representation, or check that the pairing terms commute with the IST operator; without this verification the valley-Euler/Euler classification and the subsequent domain-wall and braiding results do not follow.
- [Domain-wall modes subsection] The statement that Euler topology produces mirror-symmetry-protected helical domain-wall modes needs an explicit symmetry argument or invariant calculation (e.g., a mirror-resolved Euler number or Pfaffian invariant along the domain wall). If this is only asserted from bulk topology without a domain-wall calculation, the claim is not yet load-bearing.
minor comments (2)
- [Introduction] Define 'valley-Euler' versus 'Euler' topology at first use and clarify whether the former is a standard term or a new designation for the valley-contrasting Euler class.
- [Figures] Ensure all figures showing band structures or topological invariants are labeled with the specific pairing (SWSS or FWST) and include the IST operator action if relevant.
Simulated Author's Rebuttal
We thank the referee for their thorough review and insightful comments on our manuscript. We have carefully considered the major comments and revised the manuscript accordingly to provide the requested explicit verifications and calculations. Our point-by-point responses are as follows.
read point-by-point responses
-
Referee: [Abstract and BdG Hamiltonian section] The central claims require that both the SWSS and FWST order parameters preserve IST symmetry in the BdG Hamiltonian so that the bands remain real and admit a well-defined Euler class. The abstract asserts IST symmetry of the lattices but supplies no explicit commutation relation, matrix representation, or check that the pairing terms commute with the IST operator; without this verification the valley-Euler/Euler classification and the subsequent domain-wall and braiding results do not follow.
Authors: We agree with the referee that an explicit verification of IST symmetry preservation is essential for the validity of the Euler classification. In the revised manuscript, we have added a dedicated subsection in the BdG Hamiltonian section detailing the IST operator in matrix form for the honeycomb lattice. We explicitly demonstrate that [IST, H] = 0 for the normal state and show that both the SWSS and FWST pairing terms commute with the IST operator, preserving the reality of the bands and allowing the Euler class to be defined. The commutation relations are now provided explicitly, along with the basis choice that makes the Hamiltonian real. revision: yes
-
Referee: [Domain-wall modes subsection] The statement that Euler topology produces mirror-symmetry-protected helical domain-wall modes needs an explicit symmetry argument or invariant calculation (e.g., a mirror-resolved Euler number or Pfaffian invariant along the domain wall). If this is only asserted from bulk topology without a domain-wall calculation, the claim is not yet load-bearing.
Authors: We thank the referee for pointing this out. While the bulk-boundary correspondence for Euler topology suggests the presence of protected modes, we acknowledge the need for a more explicit argument. In the revision, we have included a symmetry analysis showing that the mirror symmetry commutes with the Euler class in a way that protects helical modes at the domain wall. Furthermore, we have added a calculation of the domain-wall spectrum using a ribbon geometry, confirming the existence of helical modes crossing the gap, protected by the mirror symmetry. We also discuss the mirror-resolved Euler invariant to make the protection rigorous. revision: yes
Circularity Check
No circularity: derivation applies standard Euler classification to IST-symmetric BdG Hamiltonians
full rationale
The paper assumes IST symmetry for the superconducting honeycomb lattices and classifies SWSS and FWST pairings as inducing valley-Euler or Euler topology via standard band-structure analysis in the BdG framework. No step reduces a claimed prediction or topological invariant to a fitted parameter defined by the result itself, nor does any load-bearing premise collapse to a self-citation chain or self-definitional loop. The helical modes and braiding follow from the topology once the symmetry is granted; the symmetry preservation is an input assumption rather than an output derived from the Euler class. The work therefore remains self-contained against external benchmarks of symmetry-protected topology.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption The system possesses space-time inversion (IST) symmetry.
Lean theorems connected to this paper
-
IndisputableMonolith/Foundation/AlexanderDuality.leanalexander_duality_circle_linking echoes?
echoesECHOES: this paper passage has the same mathematical shape or conceptual pattern as the Recognition theorem, but is not a direct formal dependency.
Electronic bands in systems with space-time inversion (IST) symmetry can host nontrivial Euler topology... χ=1/2π∫Eu(k)dkx dky where Eu(k)=∇ku1(k)×∇ku2(k)
-
IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
BdG Hamiltonian H_SC(k)=t1 h1(k)σx τz + ... + Δ η(k) τx with SWSS (Δ=ds) and FWST (Δ=df h4(k)) pairings
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
1 (e–f)), we obtainχ Dr = 1for FWST andχ Dr = 0for SWSS
Consistently, on a patch encircling both nodes (e.g., the red patchD r in Fig. 1 (e–f)), we obtainχ Dr = 1for FWST andχ Dr = 0for SWSS. 3 Δ(r) -Δ0 Δ0 ky ky ky (b) SWSS (c) FWST (a) (d) T2DEG E(t1) ●MDW=+1 E(t1) E(t1) ●MDW=-1 FIG. 2. (a) Domain-wall setup, where the sign of the pairing poten- tial flips across the domain wall. The domain-wall energy spectr...
work page 2023
-
[2]
Y . X. Zhao and Y . Lu,pt-symmetric real dirac fermions and semimetals, Phys. Rev. Lett.118, 056401 (2017)
work page 2017
-
[3]
J. Ahn and B.-J. Yang, Unconventional topological phase tran- sition in two-dimensional systems with space-time inversion symmetry, Phys. Rev. Lett.118, 156401 (2017)
work page 2017
-
[4]
J. Ahn, S. Park, and B.-J. Yang, Failure of nielsen-ninomiya theorem and fragile topology in two-dimensional systems with space-time inversion symmetry: Application to twisted bilayer graphene at magic angle, Phys. Rev. X9, 021013 (2019)
work page 2019
-
[5]
S. Kwon and B.-J. Yang, Quantum geometric bound and ideal condition for euler band topology, Phys. Rev. B109, L161111 (2024)
work page 2024
- [6]
-
[7]
J. Yu, M. Xie, F. Wu, and S. Das Sarma, Euler-obstructed nematic nodal superconductivity in twisted bilayer graphene, Phys. Rev. B107, L201106 (2023)
work page 2023
-
[8]
Z. Song, Z. Wang, W. Shi, G. Li, C. Fang, and B. A. Bernevig, All magic angles in twisted bilayer graphene are topological, Phys. Rev. Lett.123, 036401 (2019)
work page 2019
-
[9]
S. H. Lee, Y . Qian, and B.-J. Yang, Euler band topology in spin-orbit coupled magnetic systems, Phys. Rev. B111, 245127 (2025)
work page 2025
-
[10]
H. Park, S. Wong, A. Bouhon, R.-J. Slager, and S. S. Oh, Topo- logical phase transitions of non-abelian charged nodal lines in spring-mass systems, Phys. Rev. B105, 214108 (2022)
work page 2022
-
[11]
Ezawa, Topological euler insulators and their electric cir- cuit realization, Phys
M. Ezawa, Topological euler insulators and their electric cir- cuit realization, Phys. Rev. B103, 205303 (2021)
work page 2021
-
[12]
F. N. ¨Unal, A. Bouhon, and R.-J. Slager, Topological euler class as a dynamical observable in optical lattices, Phys. Rev. Lett.125, 053601 (2020)
work page 2020
-
[13]
O. Breach, R.-J. Slager, and F. N. ¨Unal, Interferometry of non- abelian band singularities and euler class topology, Phys. Rev. Lett.133, 093404 (2024)
work page 2024
-
[14]
W. Zhao, Y .-B. Yang, Y . Jiang, Z. Mao, W. Guo, L. Qiu, G. Wang, L. Yao, L. He, Z. Zhou, Y . Xu, and L. Duan, Quan- tum simulation for topological euler insulators, Communica- tions Physics5, 223 (2022)
work page 2022
-
[15]
K. Wang, J.-X. Dai, L. B. Shao, S. A. Yang, and Y . X. Zhao, Boundary criticality ofPT-invariant topology and second- order nodal-line semimetals, Phys. Rev. Lett.125, 126403 (2020)
work page 2020
-
[16]
R. Takahashi and T. Ozawa, Bulk-edge correspondence of stiefel-whitney and euler insulators through the entanglement spectrum and cutting procedure, Phys. Rev. B108, 075129 (2023)
work page 2023
- [17]
-
[18]
Q. Wu, A. A. Soluyanov, and T. Bzdu ˇsek, Non-abelian band topology in noninteracting metals, Science365, 1273 (2019), https://www.science.org/doi/pdf/10.1126/science.aau8740
-
[19]
T. Jiang, R.-Y . Zhang, Q. Guo, B. Yang, and C. T. Chan, Two- dimensional non-abelian topological insulators and the corre- sponding edge/corner states from an eigenvector frame rota- tion perspective, Phys. Rev. B106, 235428 (2022)
work page 2022
- [20]
- [21]
-
[22]
H. Qiu, Q. Zhang, T. Liu, X. Fan, F. Zhang, and C. Qiu, Mini- mal non-abelian nodal braiding in ideal metamaterials, Nature Communications14, 1261 (2023)
work page 2023
-
[23]
B. Peng, A. Bouhon, B. Monserrat, and R.-J. Slager, Phonons as a platform for non-abelian braiding and its manifestation in layered silicates, Nature Communications13, 423 (2022)
work page 2022
- [24]
-
[25]
Y . Yang, B. Yang, G. Ma, J. Li, S. Zhang, and C. T. Chan, Non-abelian physics in light and sound, Science383, eadf9621 (2024), https://www.science.org/doi/pdf/10.1126/science.adf9621
-
[26]
J. Ahn, S. Park, D. Kim, Y . Kim, and B.-J. Yang, Stiefel–whitney classes and topological phases in band theory, 6 Chinese Physics B28, 117101 (2019)
work page 2019
-
[27]
J. Ahn, D. Kim, Y . Kim, and B.-J. Yang, Band topology and linking structure of nodal line semimetals withZ 2 monopole charges, Phys. Rev. Lett.121, 106403 (2018)
work page 2018
-
[28]
W. Liu, H. Wang, B. Yang, and S. Zhang, Correspon- dence between euler charges and nodal-line topology in euler semimetals, Science Advances11, eads5081 (2025), https://www.science.org/doi/pdf/10.1126/sciadv.ads5081
-
[29]
A. Tiwari and T. c. v. Bzdu ˇsek, Non-abelian topology of nodal-line rings inPT-symmetric systems, Phys. Rev. B101, 195130 (2020)
work page 2020
-
[30]
S. Park, Y . Hwang, H. C. Choi, and B.-J. Yang, Topolog- ical acoustic triple point, Nature Communications12, 6781 (2021)
work page 2021
-
[31]
W. J. Jankowski, A. S. Morris, Z. Davoyan, A. Bouhon, F. N. ¨Unal, and R.-J. Slager, Non-abelian hopf-euler insula- tors, Phys. Rev. B110, 075135 (2024)
work page 2024
-
[32]
A. Bouhon, Y .-Q. Zhu, R.-J. Slager, and G. Palumbo, Second euler number in four-dimensional matter, Phys. Rev. B110, 195144 (2024)
work page 2024
-
[33]
Y . Guan, A. Bouhon, and O. V . Yazyev, Landau levels of the euler class topology, Phys. Rev. Res.4, 023188 (2022)
work page 2022
- [34]
-
[35]
H. Lim, S. Kim, and B.-J. Yang, Real hopf insulator, Phys. Rev. B108, 125101 (2023)
work page 2023
-
[36]
W. J. Jankowski, M. Noormandipour, A. Bouhon, and R.-J. Slager, Disorder-induced topological quantum phase transi- tions in multigap euler semimetals, Phys. Rev. B110, 064202 (2024)
work page 2024
-
[37]
B. Peng, A. Bouhon, R.-J. Slager, and B. Monserrat, Multi- gap topology and non-abelian braiding of phonons from first principles, Phys. Rev. B105, 085115 (2022)
work page 2022
-
[38]
D. Li, C. Wang, and H. Huang, Real-space approach for the Euler class and fragile topology in quasicrystals and amor- phous lattices, SciPost Phys.17, 086 (2024)
work page 2024
-
[39]
J.-T. Wang, J.-X. Liu, H.-T. Ding, and P. He, Proposal for im- plementing stiefel-whitney insulators in an optical raman lat- tice, Phys. Rev. A109, 053314 (2024)
work page 2024
- [40]
-
[41]
Measuring non-Abelian quantum geometry and topology in a multi-gap photonic lattice
M. Guillot, C. Blanchard, M. Morassi, A. Lema ˆıtre, L. L. Gratiet, A. Harouri, I. Sagnes, R.-J. Slager, F. N. ¨Unal, J. Bloch, and S. Ravets, Measuring non-abelian quantum ge- ometry and topology in a multi-gap photonic lattice (2025), arXiv:2511.03894 [cond-mat.mes-hall]
work page internal anchor Pith review Pith/arXiv arXiv 2025
-
[42]
R. Ghadimi, C. Mondal, S. Kim, and B.-J. Yang, Quantum valley hall effect without berry curvature, Phys. Rev. Lett.133, 196603 (2024)
work page 2024
- [43]
-
[44]
A. S. Morris, A. Bouhon, and R.-J. Slager, Andreev reflection in euler materials, New Journal of Physics26, 023014 (2024)
work page 2024
-
[45]
S. Kobayashi, M. Sato, and A. Furusaki, Euler band topology in superfluids and superconductors (2025), arXiv:2509.06406 [cond-mat.supr-con]
-
[46]
E. Pangburn, L. Haurie, A. Cr ´epieux, O. A. Awoga, A. M. Black-Schaffer, C. P ´epin, and C. Bena, Superconductivity in monolayer and few-layer graphene. i. review of possible pair- ing symmetries and basic electronic properties, Phys. Rev. B 108, 134514 (2023)
work page 2023
-
[47]
A. M. Black-Schaffer and C. Honerkamp, Chiral d-wave su- perconductivity in doped graphene, Journal of Physics: Con- densed Matter26, 423201 (2014)
work page 2014
-
[48]
B. Uchoa and A. H. Castro Neto, Superconducting states of pure and doped graphene, Phys. Rev. Lett.98, 146801 (2007)
work page 2007
-
[49]
L.-Y . Xiao, S.-L. Yu, W. Wang, Z.-J. Yao, and J.-X. Li, Possi- ble singlet and triplet superconductivity on honeycomb lattice, Europhysics Letters115, 27008 (2016)
work page 2016
- [50]
-
[51]
and and, Intra-valley spin-triplet p + ip superconducting pair- ing in lightly doped graphene, Chinese Physics Letters30, 017401 (2013)
work page 2013
-
[52]
K. Lee, T. Hazra, M. Randeria, and N. Trivedi, Topological superconductivity in dirac honeycomb systems, Phys. Rev. B 99, 184514 (2019)
work page 2019
- [53]
-
[54]
R. Ghadimi and B.-J. Yang, Quasiperiodic pairing in graphene quasicrystals, Nano Letters25, 1808 (2025), pMID: 39869562, https://doi.org/10.1021/acs.nanolett.4c04386
-
[55]
R. Ghadimi, S. H. Lee, and B.-J. Yang, Boundary-obstructed topological superconductor in buckled honeycomb lattice un- der perpendicular electric field, Phys. Rev. B107, 224511 (2023)
work page 2023
-
[56]
T. Li, M. Geier, J. Ingham, and H. D. Scammell, Higher-order topological superconductivity from repulsive interactions in kagome and honeycomb systems, 2D Materials9, 015031 (2021)
work page 2021
-
[57]
V . o. T. Phong, H. Sainz-Cruz, E. J. Mele, and F. Guinea, Mirror-protected majorana zero modes inf-wave multilayer graphene superconductors, Phys. Rev. B110, L100501 (2024)
work page 2024
-
[58]
X. Du, I. Skachko, and E. Y . Andrei, Josephson current and multiple andreev reflections in graphene sns junctions, Phys. Rev. B77, 184507 (2008)
work page 2008
-
[59]
A. Shailos, W. Nativel, A. Kasumov, C. Collet, M. Ferrier, S. Gu ´eron, R. Deblock, and H. Bouchiat, Proximity effect and multiple andreev reflections in few-layer graphene, Eu- rophysics Letters79, 57008 (2007)
work page 2007
-
[60]
H. B. Heersche, P. Jarillo-Herrero, J. B. Oostinga, L. M. K. Vandersypen, and A. F. Morpurgo, Bipolar supercurrent in graphene, Nature446, 56 (2007)
work page 2007
- [61]
- [62]
-
[63]
F. D. M. Haldane, Model for a quantum hall effect without landau levels: Condensed-matter realization of the ”parity anomaly”, Phys. Rev. Lett.61, 2015 (1988)
work page 2015
- [64]
- [65]
-
[66]
J.-W. Dong, X.-D. Chen, H. Zhu, Y . Wang, and X. Zhang, Val- ley photonic crystals for control of spin and topology, Nature Materials16, 298 (2017). 7
work page 2017
-
[67]
J. Noh, S. Huang, K. P. Chen, and M. C. Rechtsman, Observa- tion of photonic topological valley hall edge states, Phys. Rev. Lett.120, 063902 (2018)
work page 2018
-
[68]
J. Lu, C. Qiu, W. Deng, X. Huang, F. Li, F. Zhang, S. Chen, and Z. Liu, Valley topological phases in bilayer sonic crystals, Phys. Rev. Lett.120, 116802 (2018)
work page 2018
-
[69]
H.-X. Wang, G.-Y . Guo, and J.-H. Jiang, Band topology in classical waves: Wilson-loop approach to topological num- bers and fragile topology, New Journal of Physics21, 093029 (2019)
work page 2019
-
[70]
G. W. Semenoff, V . Semenoff, and F. Zhou, Domain walls in gapped graphene, Phys. Rev. Lett.101, 087204 (2008)
work page 2008
-
[71]
F. Zhang, A. H. MacDonald, and E. J. Mele, Valley chern numbers and boundary modes in gapped bilayer graphene, Proceedings of the Na- tional Academy of Sciences110, 10546 (2013), https://www.pnas.org/doi/pdf/10.1073/pnas.1308853110
-
[72]
M. Saba, S. Wong, M. Elman, S. S. Oh, and O. Hess, Nature of topological protection in photonic spin and valley hall insu- lators, Phys. Rev. B101, 054307 (2020)
work page 2020
-
[73]
K. Qian, D. J. Apigo, C. Prodan, Y . Barlas, and E. Prodan, Topology of the valley-chern effect, Phys. Rev. B98, 155138 (2018)
work page 2018
-
[74]
W. A. Benalcazar, B. A. Bernevig, and T. L. Hughes, Quan- tized electric multipole insulators, Science357, 61 (2017), https://www.science.org/doi/pdf/10.1126/science.aah6442
-
[75]
F. Schindler, A. M. Cook, M. G. Vergniory, Z. Wang, S. S. P. Parkin, B. A. Bernevig, and T. Neupert, Higher-order topo- logical insulators, Science Advances4, eaat0346 (2018), https://www.science.org/doi/pdf/10.1126/sciadv.aat0346
-
[76]
Y . Kim, K. Choi, J. Ihm, and H. Jin, Topological domain walls and quantum valley hall effects in silicene, Phys. Rev. B89, 085429 (2014)
work page 2014
-
[77]
H. Li, Z. Wang, Z. Wang, C. Deng, J. Luo, J. Huang, X. Wang, and H. Yang, Acoustic multichannel transports of valley edge states in bilayer sonic crystals, Applied Physics Let- ters121, 243101 (2022), https://pubs.aip.org/aip/apl/article- pdf/doi/10.1063/5.0127559/16487480/243101 1 online.pdf
-
[78]
Z. Wang, S. Cheng, X. Liu, and H. Jiang, Topological kink states in graphene, Nanotechnology32, 402001 (2021)
work page 2021
- [79]
-
[80]
S.-H. Han, M. Kang, M. J. Park, and S. Cheon, Quantized polarization and majorana fermions beyond tenfold classifica- tion, Communications Physics7, 243 (2024)
work page 2024
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.