Pith. sign in

REVIEW 3 major objections 4 minor 55 references

Topological surface altermagnets in SSH-stacked magnetic layers

T0 review · 3 major / 4 minor · reviewed 2026-08-10 · deepseek-v4-flash

Pith's one-line read A stack of alternating magnetic layers ordered like an SSH chain produces a topologically protected surface altermagnet, with the bulk remaining a spin-degenerate antiferromagnet.

desk verdict A clean SSH-stacking model for surface altermagnetism with an overstated topological-protection claim; the exact edge-state calculation is right, but the robustness story needs to be narrowed. read the letter →

arxiv 2608.07099 v1 pith:WGRTK7S3 submitted 2026-08-07 cond-mat.mes-hall

classification cond-mat.mes-hall
keywords topologicalsurfacealtermagnetismSu-Schrieffer-Heegermodelantiferromagnetspinsplittereffectd-wavesplittingstateselectric-fielddetectionhiddenaltermagnet
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

The paper proposes a scheme to create surface altermagnetism in a conventional antiferromagnet by stacking two-dimensional magnetic layers in a Su-Schrieffer-Heeger (SSH) sequence of alternating interlayer bonds. In the bulk, adjacent layers are parity-times-time-reversal partners with opposite altermagnetic spin splittings, so the bands remain spin-degenerate and the bulk looks like an ordinary compensated antiferromagnet. Cutting the stack breaks this local symmetry and leaves an uncompensated altermagnetic layer at the boundary, whose surface states are topologically protected inside the gap. The authors show that at each in-plane momentum the model is an SSH chain, and the boundary modes shift by exactly ±2J(cos kx − cos ky), producing a d-wave surface altermagnet that persists for finite intra-layer hopping; the same stacking idea works for p- and f-wave altermagnets. They further propose detecting the surface states through a layer-resolved spin-splitter angle and a perpendicular electric field that unbalances the two surfaces.

What carries the argument

The load-bearing object is the SSH-stacked Hamiltonian H(k) = ((h(k∥), t1 + t2 $e^{{−ikz}}$); (t1 + t2 $e^{{ikz}}$, h′(k∥))) with h(′)(k∥) = 2t(cos kx + cos ky)s0 ± 2J(cos kx − cos ky)sz. At fixed in-plane momentum the two layers of each unit cell form the two sublattices of an SSH chain, and the bulk PT symmetry pairs them so that the bands are spin-degenerate. The topological content is captured by the Zak phase along the nodal lines where the altermagnetic term vanishes, which is quantized to 0 or π depending on t1/t2; moving away from the nodes, the chiral-symmetry-breaking term ±2J(cos kx − cos ky) shifts the boundary modes by exactly that amount. The surface altermagnet is thus the continuous, momentum-resolved collection of SSH zero modes dressed by the in-plane altermagnetic splitting.

What would settle it

A slab calculation for a real material candidate (for instance a van der Waals stack with alternating interlayer spacings) that finds the bulk bands spin-split, or finds the surface states not following the ±2J(cos kx − cos ky) pattern, would show that the exact PT-pairing assumption fails; equally, measuring the surface spin-splitter angle and seeing no signal in the nontrivial regime t1 < t2 would directly falsify the claimed topological surface altermagnetism.

Watch

Extended reading notes

Core claim

The central claim is that geometric truncation of an SSH-stacked magnetic multilayer converts an ordinary, spin-degenerate antiferromagnet into a topological surface altermagnet. The bulk Hamiltonian contains two layer blocks that are PT partners carrying opposite altermagnetic splittings ±2J(cos kx − cos ky)sz, so the combined system is PT-symmetric and spin-degenerate. At an open boundary the local PT symmetry is lost, leaving an uncompensated layer whose altermagnetic character shows up as spin-split surface states. Because in-plane momentum is conserved, the stack decouples into independent SSH chains, and when the interlayer hoppings satisfy t1 < t2 these chains are topologically nontrivial: their zero-energy boundary modes, protected by chiral symmetry along the nodal lines kx = ±ky, are shifted by the exact amplitude ±2J(cos kx − cos ky) away from the nodes. The continuous family of these shifted boundary modes across the Brillouin zone is the d-wave surface altermagnet, and it remains well-defined within the direct bulk gap even when a uniform in-plane hopping adds dispersion. The same mechanism is shown for p- and f-wave altermagnetic layers, establishing topological boundaries as a general platform for surface altermagnetism.

Load-bearing premise

The scheme assumes each unit cell contains two layers that are exact PT partners with opposite altermagnetic spin splitting, and that a clean surface termination leaves one uncompensated layer at the boundary; if real interlayer coupling mixes the two orders or surface reconstruction removes the uncompensated layer, the bulk is not a clean compensated antiferromagnet and the surface state loses its altermagnetic character.

Editorial extensions

If this is right

  • A surface altermagnet can be engineered from any conventional antiferromagnet by arranging its layers in an alternating-bond SSH stack, without needing bulk altermagnetic order.
  • The surface spin-split states remain inside the direct bulk gap and localized at the boundary for finite intra-layer hopping, and they disappear entirely in the trivial regime t1 > t2.
  • Applying a perpendicular electric field destroys the exact cancellation between top and bottom surfaces and produces a net, angle-dependent spin-splitter signal, giving a measurable transport signature.
  • The same stacking design with p- or f-wave altermagnetic layers yields correspondingly different surface spin textures, showing that the topological mechanism is not restricted to d-wave order.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Because the boundary-mode shift equals the single-layer term ±2J(cos kx − cos ky), the surface spin splitting is essentially set by the layer's intrinsic exchange coupling J, independent of the topological gap size; this suggests the surface altermagnetism could be tuned by choosing or straining the magnetic layer.
  • Since the topological protection is per-k∥ SSH chains, weak disorder that scatters between momenta could in principle degrade the surface spin polarization; an interesting test would be to add finite in-plane impurity scattering and check whether the d-wave spin texture survives.
  • The dependence of the surface state on the ratio t1/t2 implies that the same stacking geometry could serve as a topological switch: changing the interlayer bond order (e.g., by pressure or by inserting a spacer) would turn surface altermagnetism on or off without changing the magnetic order.
Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 4 minor

Summary. The paper proposes a tight-binding construction in which two-dimensional altermagnetic layers are stacked in a Su-Schrieffer-Heeger pattern. The two layers per unit cell are PT partners with opposite altermagnetic spin splittings, so the bulk is a compensated, spin-degenerate antiferromagnet. At an open boundary the local PT symmetry is broken, and the authors show numerically and analytically that edge modes appear inside the bulk gap with energies shifted by ±2J(cos kx - cos ky); the surface spin-resolved LDOS, the layer-resolved spin splitter angle, and a proposed perpendicular-electric-field detection scheme are presented. The mechanism is generalized to p-wave and f-wave altermagnetic layers. The central advertised claim is that these surface altermagnetic states are topologically protected.

Significance. If fully established, the paper would offer a simple design principle for surface altermagnetism in artificial multilayers and van der Waals stacks, and it connects the recent surface-altermagnetism literature with textbook SSH topology. The strengths are that the exact energy shift of the boundary modes follows from the sublattice polarization of the SSH edge states, and the numerical spectra and LDOS in Figs. 1-3 support the existence of strongly spin-polarized boundary states within the model. The paper is not fitted to any material and the topological-protection assertion is the main point of concern.

major comments (3)
  1. [Topological nature] The central claim that the surface altermagnet is topologically protected is not supported by the presented argument. The Zak-phase argument is valid only on the nodal lines kx=±ky, where the ±2J(cos kx - cos ky)sz term vanishes. At a generic in-plane momentum, after removing the scalar energy shift, the 1D Hamiltonian per spin sector has the form m(k∥)σz + [t1 + t2 e^{-ikz}]σ+ + h.c., which has no chiral symmetry; hence no quantized Zak phase protects its boundary modes. The exact edge states at E=ε±m exist because the SSH zero modes are sublattice-pure, not because of a topological invariant. Adiabatic connection to the nodal-line zero modes does not imply robustness: a perturbation that mixes the two sublattices at the surface can move these states off ε±m without closing the bulk gap. I recommend either deriving a genuine invariant for the full Brillouin zone, for example by exploiting the exact pseudo-chiral relation C[H(k)-ε(k∥)I]C^{-1}=-[H(k)-ε(k∥)I], or substantially revising the title, abstract, and conclusion so that they claim exact but not generically topologically protected surface states.
  2. [Model and dimerized limit] The construction in Eq. (1) assumes that the two layers in each unit cell are exact PT partners with opposite altermagnetic splittings, and that the surface termination leaves an uncompensated layer in the dimerized limit or a sublattice-pure boundary mode for t1≠0. If a realistic material has spin-dependent interlayer hybridization, interlayer exchange, or surface reconstruction, the sublattice purity is lost and the exact ±2J(cos kx - cos ky) shift ceases to be an eigenstate property. This is a structural limitation of the model; it should be stated explicitly, and the robustness claim should be tested against a perturbation that directly couples the two sublattices at the boundary.
  3. [Layer-resolved spin splitter effect] The total spin splitter angle is defined as α(θ)=Σ_z α(z,θ), where each α(z,θ) is 2 arctan[(σ↑-σ↓)/(σ↑+σ↓)] for a single layer. Summing per-layer arctangents is not generally equivalent to the spin splitter angle computed from the total spin and charge conductivities, which would be 2 arctan[Σ_z(σ↑-σ↓)/Σ_z(σ↑+σ↓)]. Since the electric-field detection prediction in Fig. 2 relies on this total quantity, the summation formula should be justified or replaced by the conductivity-weighted total response.
minor comments (4)
  1. [Generalization to more scenarios] The text says 'p-wave and g-wave altermagnetism' but the model and Fig. 3 are for p-wave and f-wave; please correct this inconsistency.
  2. [Supplementary Material] The proof of the exact ±2J(cos kx - cos ky) shift is relegated to the Supplementary Material; since this is the main analytic result, a sketch of the sublattice-polarization argument should appear in the main text.
  3. [Layer-resolved spin splitter effect] The layer-dependent potential is written as V_z = V(2z - Nz -1)/(Nz -1), but the parentheses and typesetting are ambiguous; the formula should be clarified.
  4. [Layer-resolved spin splitter effect] In the definition of α(z,θ), the text refers to the 'j-th layer' although the variable is z; this should be corrected.

Circularity Check

1 steps flagged · score 4.0 of 10

The surface d-wave altermagnetic spin pattern is an input restatement (exposed altermagnetic layer), while the SSH topological-gap survival is independently derived; overall partial circularity.

  1. self definitional [Model (Eq. 1) and 'The emergent surface altermagnetism', dimerized-limit paragraph]
    "Crucially, the individual layer Hamiltonian h(k∥) or h′(k∥) inherently breaks the PT symmetry, hosting an altermagnetic state. [Model] ... This isolated surface layer breaks the local PT symmetry, thereby constituting a surface altermagnet. [Emergent surface altermagnetism]"

    The intralayer blocks in Eq. (1) are defined as 2t(coskx+cosky)s0 ± 2J(coskx−cosky)sz, so altermagnetic spin splitting is an input, not a derived output. After truncation, the surface layer is one of these uncompensated altermagnetic layers; thus the predicted d-wave surface spin polarization (Figs. 1d, 1e, 2a) is exactly the input ±2J(coskx−cosky) pattern restated by construction. The independent, noncircular content is the SSH boundary-mode mechanism at kx=±ky and the presence of the shifted states in the gap for t1<t2; but the 'surface altermagnetism' label itself reduces to the definition of the constituent layers.

full rationale

The central derivation is self-contained in the sense that no parameters are fitted to experimental data and the surface-state energies are computed from the explicit model. The topological argument at kx=±ky uses the standard external SSH chiral-symmetry/Zak-phase result, and the papers cited for that (36, 46, 47, 49, 50, 51) are textbook/external. The several self-citations (23, 24, 39, 53, and 35 via coauthor B. Zhou) are used only for background or for an experimental-detection analogy and are not load-bearing for the claim. The main circularity is definitional: the model begins with altermagnetic layers, so the exposed surface layer is an altermagnet by construction, and the d-wave surface spin-splitting pattern is a restatement of the input ±2J(coskx−cosky)sz term. That said, the topological survival of the shifted modes in the nontrivial dimerization regime is derived, not assumed, so the paper has substantial independent content. I do not count the unproven 'adiabatically connected' protection at generic momenta as circularity, since that is a correctness/rigor concern rather than a reduction to inputs.

Assumptions & free parameters 3 free parameters · 4 assumptions · 0 invented entities

The central claim rests on the tight-binding model in Eq. (1), the PT-partner assumption, and the SSH topology. No new entities are introduced and no parameters are fitted to experiments; the free parameters are hand-set model couplings.

free parameters (3)
  • interlayer hoppings t1 and t2 = t1=0.5, t2=1
    Chosen to put the system in the topologically nontrivial regime t1<t2 of the SSH model; not fitted to material data.
  • intralayer exchange coupling J = J=0.05
    Sets the altermagnetic spin-splitting magnitude; chosen small relative to hopping to keep a gap.
  • intralayer hopping t = t=0 and t=1 in the two numerical cases
    Controls in-plane dispersion; chosen to illustrate the effect with and without the t term.
assumptions (4)
  • domain assumption The two intralayer Hamiltonians h and h' are exact PT partners, making the bulk spin-degenerate antiferromagnet.
    Invoked after Eq. (1); if the layers are not exact partners, the bulk would have net spin splitting.
  • domain assumption The interlayer couplings alternate as t1,t2 and can be engineered in artificial multilayers or van der Waals heterostructures.
    Paragraph after Eq. (1); the whole proposal depends on the feasibility of controlled SSH stacking.
  • standard math Along kx=±ky, the Hamiltonian reduces to the pristine SSH model with quantized Zak phase 0 or pi.
    Used in the topological nature section to justify the boundary modes; standard SSH result.
  • standard math The edge-mode energy shift equals exactly ±2J(cos kx - cos ky) because the SSH edge state is sublattice-polarized.
    Stated with proof deferred to supplementary SI; underlies the d-wave spin pattern.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Topological surface altermagnets in SSH-stacked magnetic layers." pith.science (2026). https://pith.science/paper/WGRTK7S3

@misc{pith2026260807099,
  author       = {Pith},
  title        = {Pith review of: Topological surface altermagnets in SSH-stacked magnetic layers},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/WGRTK7S3}},
  note         = {Machine review of arXiv:2608.07099}
}
abstract

Surface altermagnetism opens new avenues in spintronics by unlocking altermagnetic spin-splitting at the boundaries of conventional antiferromagnets, bypassing the strict symmetry requirements of bulk altermagnets. In this work, we propose creating topological surface altermagnet by stacking magnetic layers in a Su-Schrieffer-Heeger pattern. We show that while the bulk of the system is a standard antiferromagnet with degenerate bands protected by $PT$ symmetry, breaking the local symmetry at the boundary gives rise to a topologically protected surface altermagnetic state residing within the topological gap. Furthermore, we propose that this effect can be experimentally detected by applying a perpendicular electric field. Besides, this approach can be readily generalized to surface altermagnetism of different types. Our work establishes topological boundaries as a natural platform for surface altermagnetism, offering a distinct route for realizing and manipulating topological surface altermagnets.

Figures

Figures reproduced from arXiv: 2608.07099 by the authors.

Figure 1
Figure 1. FIG. 1. (a) Schematic illustration of the SSH stacking of [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗
Figure 2
Figure 2. FIG. 2. Transport signatures and surface spin polarization of [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. FIG. 3. Generalization of topological surface altermagnetism [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

55 extracted references · 43 canonical work pages

  1. [1]

    Beyond con- ventional ferromagnetism and antiferromagnetism: A phase with nonrelativistic spin and crystal rotation sym- 5 metry

    L. ˇSmejkal, J. Sinova, and T. Jungwirth, “Beyond con- ventional ferromagnetism and antiferromagnetism: A phase with nonrelativistic spin and crystal rotation sym- 5 metry”, Phys. Rev. X12, 031042 (2022)

  2. [2]

    Altermagnetism: Exploring new frontiers in magnetism and spintronics

    L. Bai, W. Feng, S. Liu, L. ˇSmejkal, Y. Mokrousov, and Y. Yao, “Altermagnetism: Exploring new frontiers in magnetism and spintronics”, Adv. Funct. Mater. , 2409327 (2024)

  3. [3]

    Spin current generation in organic antiferromagnets

    M. Naka, S. Hayami, H. Kusunose, Y. Yanagi, Y. Mo- tome, and H. Seo, “Spin current generation in organic antiferromagnets”, Nat. Commun.10, 4305 (2019)

  4. [4]

    Anti- ferromagnetism in RuO 2 asd-wave Pomeranchuk insta- bility

    K.-H. Ahn, A. Hariki, K.-W. Lee, and J. Kuneˇ s, “Anti- ferromagnetism in RuO 2 asd-wave Pomeranchuk insta- bility”, Phys. Rev. B99, 184432 (2019)

  5. [5]

    Momentum- dependent spin splitting by collinear antiferromagnetic ordering

    S. Hayami, Y. Yanagi, and H. Kusunose, “Momentum- dependent spin splitting by collinear antiferromagnetic ordering”, J. Phys. Soc. Jpn.88, 123702 (2019)

  6. [6]

    Giant momentum-dependent spin splitting in centrosymmetric low-zantiferromagnets

    L.-D. Yuan, Z. Wang, J.-W. Luo, E. I. Rashba, and A. Zunger, “Giant momentum-dependent spin splitting in centrosymmetric low-zantiferromagnets”, Phys. Rev. B102, 014422 (2020)

  7. [7]

    Prediction of unconven- tional magnetism in doped FeSb2

    I. I. Mazin, K. Koepernik, M. D. Johannes, R. Gonz´ alez- Hern´ andez, and L. ˇSmejkal, “Prediction of unconven- tional magnetism in doped FeSb2”, Proc. Nat. Acad. Sci. 118, e2108924118 (2021)

  8. [8]

    Multifunctional antiferromagnetic materi- als with giant piezomagnetism and noncollinear spin cur- rent

    H.-Y. Ma, M. Hu, N. Li, J. Liu, W. Yao, J.-F. Jia, and J. Liu, “Multifunctional antiferromagnetic materi- als with giant piezomagnetism and noncollinear spin cur- rent”, Nat. Commun.12, 2846 (2021)

Show all 55 references
  1. [9]

    Emerging re- search landscape of altermagnetism

    L. ˇSmejkal, J. Sinova, and T. Jungwirth, “Emerging re- search landscape of altermagnetism”, Phys. Rev. X12, 040501 (2022)

  2. [10]

    Altermagnetic lifting of kramers spin degeneracy

    J. Krempask` y, L. ˇSmejkal, S. D’souza, M. Hajlaoui, G. Springholz, K. Uhl ´ ıˇ rov´ a,et al., “Altermagnetic lifting of kramers spin degeneracy”, Nature626, 517 (2024)

  3. [11]

    Anomalous Hall antiferromagnets

    L. Smejkal, A. H. MacDonald, J. Sinova, S. Nakatsuji, and T. Jungwirth, “Anomalous Hall antiferromagnets”, Nat. Rev. Mat.7, 482 (2022)

  4. [12]

    Exploration of altermagnetism in RuO2

    Y.-X. Li, Y. Chen, L. Pan, S. Li, S.-B. Zhang, and H.-Z. Lu, “Exploration of altermagnetism in RuO2”, Sci. China Phys. Mech. Astron.69, 257001 (2026)

  5. [13]

    Perovskite as a spin current generator

    M. Naka, Y. Motome, and H. Seo, “Perovskite as a spin current generator”, Phys. Rev. B103, 125114 (2021)

  6. [14]

    Spin-neutral currents for spintronics

    D.-F. Shao, S.-H. Zhang, M. Li, C.-B. Eom, and E. Y. Tsymbal, “Spin-neutral currents for spintronics”, Nat. Commun.12, 7061 (2021)

  7. [15]

    Topological transition from nodal to nodeless zeeman splitting in altermagnets

    R. M. Fernandes, V. S. de Carvalho, T. Birol, and R. G. Pereira, “Topological transition from nodal to nodeless zeeman splitting in altermagnets”, Phys. Rev. B109, 024404 (2024)

  8. [16]

    Predictable gate-field control of spin in al- termagnets with spin-layer coupling

    R.-W. Zhang, C. Cui, R. Li, J. Duan, L. Li, Z.-M. Yu, and Y. Yao, “Predictable gate-field control of spin in al- termagnets with spin-layer coupling”, Phys. Rev. Lett. 133, 056401 (2024)

  9. [17]

    Crystal Thermal Transport in Altermagnetic RuO 2

    X. Zhou, W. Feng, R.-W. Zhang, L. ˇSmejkal, J. Sinova, Y. Mokrousov, and Y. Yao, “Crystal Thermal Transport in Altermagnetic RuO 2”, Phys. Rev. Lett.132, 056701 (2024)

  10. [18]

    Electri- cal switching of altermagnetism

    Y. Chen, X. Liu, H.-Z. Lu, and X. C. Xie, “Electri- cal switching of altermagnetism”, Phys. Rev. Lett.135, 016701 (2025)

  11. [19]

    Spectroscopic evidence of spin-state excitation in d-electron correlated semiconductor FeSb 2

    H. Li, G. Wang, N. Ding, Q. Ren, G. Zhao, W. Lin, et al., “Spectroscopic evidence of spin-state excitation in d-electron correlated semiconductor FeSb 2”, Proc. Nat. Acad. Sci.121, e2321193121 (2024)

  12. [20]

    Giant and tunneling magnetoresistance in unconventional collinear antiferro- magnets with nonrelativistic spin-momentum coupling

    L. ˇSmejkal, A. B. Hellenes, R. Gonz´ alez-Hern´ andez, J. Sinova, and T. Jungwirth, “Giant and tunneling magnetoresistance in unconventional collinear antiferro- magnets with nonrelativistic spin-momentum coupling”, Phys. Rev. X12, 011028 (2022)

  13. [21]

    Detecting the N´ eel vector of altermagnets in heterostructures with a topological insulator and a crys- talline valley-edge insulator

    M. Ezawa, “Detecting the N´ eel vector of altermagnets in heterostructures with a topological insulator and a crys- talline valley-edge insulator”, Phys. Rev. B109, 245306 (2024)

  14. [22]

    Creation and manipula- tion of higher-order topological states by altermagnets

    Y.-X. Li, Y. Liu, and C.-C. Liu, “Creation and manipula- tion of higher-order topological states by altermagnets”, Phys. Rev. B109, L201109 (2024)

  15. [23]

    Anomalous hall effects in magnetic weak topological insulator films

    R. Chen, X.-X. Yi, B. Zhou, and D.-H. Xu, “Anomalous hall effects in magnetic weak topological insulator films”, Phys. Rev. B111, 045409 (2025)

  16. [24]

    Probingk-space alternating spin polarization via the anomalous hall effect

    R. Chen, Z.-M. Wang, H.-P. Sun, B. Zhou, and D.-H. Xu, “Probingk-space alternating spin polarization via the anomalous hall effect”, arXiv:2501.14217 (2025)

  17. [25]

    Efficient spin-to-charge conversion via altermagnetic spin splitting effect in antiferromagnet ruo2

    H. Bai, Y. C. Zhang, Y. J. Zhou, P. Chen, C. H. Wan, L. Han,et al., “Efficient spin-to-charge conversion via altermagnetic spin splitting effect in antiferromagnet ruo2”, Phys. Rev. Lett.130, 216701 (2023)

  18. [26]

    Efficient electrical spin splitter based on nonrelativis- tic collinear antiferromagnetism

    R. Gonz´ alez-Hern´ andez, L.ˇSmejkal, K. V´ yborn´ y, Y. Ya- hagi, J. Sinova, T. c. v. Jungwirth, and J. ˇZelezn´ y, “Efficient electrical spin splitter based on nonrelativis- tic collinear antiferromagnetism”, Phys. Rev. Lett.126, 127701 (2021)

  19. [27]

    Crystal time-reversal symmetry breaking and spontaneous Hall effect in collinear antiferromagnets

    L. ˇSmejkal, R. Gonz´ alez-Hern´ andez, T. Jungwirth, and J. Sinova, “Crystal time-reversal symmetry breaking and spontaneous Hall effect in collinear antiferromagnets”, Sci. Adv.6, eaaz8809 (2020)

  20. [28]

    An anomalous Hall effect in altermagnetic ruthe- nium dioxide

    Z. Feng, X. Zhou, L. Smejkal, L. Wu, Z. Zhu, H. Guo, et al., “An anomalous Hall effect in altermagnetic ruthe- nium dioxide”, Nat. Elec.5, 735 (2022)

  21. [29]

    Observation of time- reversal symmetry breaking in the band structure of al- termagnetic RuO2

    O. Fedchenko, J. Minar, A. Akashdeep, S. W. DSouza, D. Vasilyev, O. Tkach,et al., “Observation of time- reversal symmetry breaking in the band structure of al- termagnetic RuO2”, Sci. Adv.10, eadj4883 (2024)

  22. [30]

    Observation of Spin-Splitter Torque in Collinear Antiferromagnetic RuO 2

    S. Karube, T. Tanaka, D. Sugawara, N. Kadoguchi, M. Kohda, and J. Nitta, “Observation of Spin-Splitter Torque in Collinear Antiferromagnetic RuO 2”, Phys. Rev. Lett.129, 137201 (2022)

  23. [31]

    Absence of magnetic order in RuO2: insights fromµSR spectroscopy and neu- tron diffraction

    P. Keßler, L. Garcia-Gassull, A. Suter, T. Prokscha, Z. Salman, D. Khalyavin,et al., “Absence of magnetic order in RuO2: insights fromµSR spectroscopy and neu- tron diffraction”, npj Spintronics2, 50 (2024)

  24. [32]

    Topologically protected surface altermagnetism on an- tiferromagnets

    V. Leeb, P. d’Ornellas, F. de Juan, and A. G. Grushin, “Topologically protected surface altermagnetism on an- tiferromagnets”, arXiv:2602.10108 (2026)

  25. [33]

    Emer- gent altermagnetism at surfaces of antiferromagnets: full symmetry classification and material identification

    C. Lange, R. Jaeschke-Ubiergo, A. Chakraborty, X. H. Verbeek, L. ˇSmejkal, J. Sinova, and A. Mook, “Emer- gent altermagnetism at surfaces of antiferromagnets: full symmetry classification and material identification”, arXiv:2602.08773 (2026)

  26. [34]

    d-wave surface al- termagnetism in centrosymmetric collinear antiferromag- nets

    E. Sasioglu, I. Mertig, and S. Lounis, “d-wave surface al- termagnetism in centrosymmetric collinear antiferromag- nets”, arXiv:2602.08790 (2026)

  27. [35]

    Emergent surface altermagnetism

    Y. Hu, P. Zhou, B. Pan, S. Liu, B. Zhou, and L. Sun, “Emergent surface altermagnetism”, Phys. Rev. Lett. (2026), 10.1103/hw4l-jknk

  28. [36]

    Solitons in polyacetylene

    W. P. Su, J. R. Schrieffer, and A. J. Heeger, “Solitons in polyacetylene”, Phys. Rev. Lett.42, 1698 (1979)

  29. [37]

    Hidden altermagnetism

    S.-D. Guo, “Hidden altermagnetism”, Frontiers of Physics21, 025201 (2026)

  30. [38]

    Multifer- roic collinear antiferromagnets with hidden altermagnetic 6 spin splitting

    J. Matsuda, H. Watanabe, and R. Arita, “Multifer- roic collinear antiferromagnets with hidden altermagnetic 6 spin splitting”, Phys. Rev. Lett.134, 226703 (2025)

  31. [39]

    Observation of hidden altermagnetism in Cs1−δV2Te2O

    G. Yang, R. Chen, C. Liu, J. Li, Z. Pan, L. Deng, et al., “Observation of hidden altermagnetism in Cs1−δV2Te2O”, arXiv:2512.00972 (2025)

  32. [40]

    Altermagnetic even-odd effects in CsV 2Te2O josephson junctions

    C. Li, J.-X. Hou, S.-L. Zhu, H. Zheng, Y. Song, Y. Liu, S.- B. Zhang, and L.-H. Hu, “Altermagnetic even-odd effects in CsV 2Te2O josephson junctions”, arXiv:2602.14485 (2026)

  33. [41]

    Symme- try classification of nonrelativistic hidden spin polariza- tion in noncollinear magnets

    Y. Hu, P. Zhou, B. Pan, P. Lyu, and L. Sun, “Symme- try classification of nonrelativistic hidden spin polariza- tion in noncollinear magnets”, Phys. Rev. Lett. (2026), 10.1103/8pg5-pz4z

  34. [42]

    Oscillations in exchange coupling and magnetoresistance in metal- lic superlattice structures: Co/Ru, Co/Cr, and Fe/Cr

    S. S. P. Parkin, N. More, and K. P. Roche, “Oscillations in exchange coupling and magnetoresistance in metal- lic superlattice structures: Co/Ru, Co/Cr, and Fe/Cr”, Phys. Rev. Lett.64, 2304 (1990)

  35. [43]

    Van der waals het- erostructures

    A. K. Geim and I. V. Grigorieva, “Van der waals het- erostructures”, Nature499, 419–425 (2013)

  36. [44]

    Giant tunneling magnetoresistance in spin-filter van der waals heterostructures

    T. Song, X. Cai, M. W.-Y. Tu, X. Zhang, B. Huang, N. P. Wilson,et al., “Giant tunneling magnetoresistance in spin-filter van der waals heterostructures”, Science360, 1214–1218 (2018)

  37. [45]

    Magnetic 2d materials and heterostruc- tures

    M. Gibertini, M. Koperski, A. F. Morpurgo, and K. S. Novoselov, “Magnetic 2d materials and heterostruc- tures”, Nature Nanotechnology14, 408–419 (2019)

  38. [46]

    Shen,Topological Insulators–Dirac Equation in Condensed Matter(Springer Singapore, 2017)

    S.-Q. Shen,Topological Insulators–Dirac Equation in Condensed Matter(Springer Singapore, 2017)

  39. [47]

    The su- schrieffer-heeger (ssh) model

    J. K. Asb´ oth, L. Oroszl´ any, and A. P´ alyi, “The su- schrieffer-heeger (ssh) model”, inA Short Course on Topological Insulators(Springer International Publish- ing, 2016) p. 1–22

  40. [48]

    See Supplemental Material for more details

  41. [49]

    B. A. Bernevig and T. L. Hughes,Topological Insulators and Topological Superconductors(Princeton University Press, 2013)

  42. [50]

    Colloquium: Topological insulators

    M. Z. Hasan and C. L. Kane, “Colloquium: Topological insulators”, Rev. Mod. Phys.82, 3045 (2010)

  43. [51]

    Topological insulators and superconductors

    X.-L. Qi and S.-C. Zhang, “Topological insulators and superconductors”, Rev. Mod. Phys.83, 1057 (2011)

  44. [52]

    Layer Hall effect in a 2D topological axion antiferromagnet

    A. Gao, Y.-F. Liu, C. Hu, J.-X. Qiu, C. Tzschaschel, B. Ghosh,et al., “Layer Hall effect in a 2D topological axion antiferromagnet”, Nature595, 521 (2021)

  45. [53]

    Layer Hall effect induced by hidden Berry curvature in antiferromagnetic insulators

    R. Chen, H.-P. Sun, M. Gu, C.-B. Hua, Q. Liu, H.-Z. Lu, and X. C. Xie, “Layer Hall effect induced by hidden Berry curvature in antiferromagnetic insulators”, Natl. Sci. Rev.11, nwac140 (2022)

  46. [54]

    Spin- to charge-current conversion in altermagnetic candidate ruo 2 probed by terahertz emission spectroscopy

    J. Jechumt´ al, O. Gueckstock, K. Jasensk´ y, Z. Kaˇ spar, K. Olejn ´ ık, M. Gaerner,et al., “Spin- to charge-current conversion in altermagnetic candidate ruo 2 probed by terahertz emission spectroscopy”, Phys. Rev. B113, 054439 (2026)

  47. [55]

    Bottom-up de- sign of spin-split and reshaped electronic band structures in antiferromagnets without spin-orbit coupling: Proce- dure on the basis of augmented multipoles

    S. Hayami, Y. Yanagi, and H. Kusunose, “Bottom-up de- sign of spin-split and reshaped electronic band structures in antiferromagnets without spin-orbit coupling: Proce- dure on the basis of augmented multipoles”, Phys. Rev. B102, 144441 (2020)

Pith tools

Reviewed August 10, 2026 · model on record in the stance chip above.