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arxiv: 2607.02114 · v1 · pith:QC3UF3PPnew · submitted 2026-07-02 · ❄️ cond-mat.str-el · cond-mat.mtrl-sci

Plaid-Like Spin Splitting and Chirality of Magnon Bands in Antiferromagnetic MnTe₂

Dirk Wulferding , Daehyeon An , Jiwon Choi , Dongmin Mun , Youngsu Choi , Sivasakthi Kuppusamy , Sritharan Krishnamoorthi , Raman Sankar
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Myung Joon Han Se Kwon Kim Kwang-Yong Choi
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Pith reviewed 2026-07-03 05:57 UTC · model grok-4.3

classification ❄️ cond-mat.str-el cond-mat.mtrl-sci
keywords magnon chiralityantiferromagnetic MnTe2Raman scatteringplaid-like spin splittingaltermagnetismspin-wave theorysublattice symmetry
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The pith

Helicity-resolved Raman scattering detects momentum-dependent magnon chirality and plaid-like spin splitting in antiferromagnetic MnTe2.

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

The paper establishes that magnon excitations in MnTe2 carry a momentum-dependent handedness arising from the material's non-coplanar antiferromagnetic order and its sublattice symmetries. Helicity- and angle-resolved Raman measurements show reduced rotational symmetry and a clear imbalance between left- and right-circular channels, while DFT+U plus linear spin-wave calculations map this imbalance onto a plaid-like splitting pattern in momentum space. The resulting magnon spin textures closely match the spin-split bands known from altermagnets even though the net magnetization remains zero. A sympathetic reader would care because the result supplies direct spectroscopic evidence that compensated antiferromagnets can host chiral spin-wave modes without external fields or net moments.

Core claim

MnTe2 hosts magnon bands whose spin splitting takes a plaid-like form in momentum space. This splitting is produced by the material's unconventional sublattice symmetries and is revealed experimentally by a pronounced imbalance between left- and right-circular Raman channels together with lowered rotational symmetry of the magnon response. First-principles DFT+U calculations combined with linear spin-wave theory reproduce the observed splitting and show that the magnon spin textures emulate the characteristic altermagnetic electronic band structure.

What carries the argument

Plaid-like spin-splitting structure in momentum space, produced by the unconventional sublattice symmetries of the non-coplanar antiferromagnet MnTe2.

If this is right

  • Magnon bands in MnTe2 carry a momentum-dependent handedness that survives the compensation of the antiferromagnetic order.
  • The observed polarization imbalance is a direct spectroscopic signature of the reduced rotational symmetries imposed by the sublattice arrangement.
  • The magnon spin texture can be computed from the same DFT+U parameters that describe the electronic altermagnetic bands.
  • Chiral magnon excitations are therefore a general feature of this class of non-coplanar antiferromagnets.

Where Pith is reading between the lines

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

  • Similar Raman signatures may appear in other non-coplanar antiferromagnets whose sublattice symmetries break the same rotational operations.
  • If the plaid splitting controls magnon transport, devices that rely on magnon chirality could be realized without external magnetic fields.
  • The same symmetry analysis could be applied to predict chiral phonon or electronic modes in isostructural compounds.
  • A direct test would be to measure whether the magnon handedness reverses when the antiferromagnetic domain is switched.

Load-bearing premise

The measured imbalance between left- and right-circular Raman channels is caused by intrinsic magnon chirality rather than by scattering geometry or non-magnetic contributions.

What would settle it

A helicity-resolved Raman map taken under identical conditions that shows equal left- and right-circular intensities across the Brillouin zone, or a spin-wave calculation that produces symmetric magnon bands without plaid splitting, would falsify the claim.

Figures

Figures reproduced from arXiv: 2607.02114 by Daehyeon An, Dirk Wulferding, Dongmin Mun, Jiwon Choi, Kwang-Yong Choi, Myung Joon Han, Raman Sankar, Se Kwon Kim, Sivasakthi Kuppusamy, Sritharan Krishnamoorthi, Youngsu Choi.

Figure 1
Figure 1. Figure 1: FIG. 1. (a) Pyrite-type crystal structure of MnTe [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. (a) and (b): Color-contour plots of polarization-resolved Raman data obtained at [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. (a) Schematic picture of the symmetric points in the Brillouin zone. Magnon energy bands of the MnTe [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
read the original abstract

Altermagnets constitute an emerging class of magnetic materials that combine compensated antiferromagnetic order with spin-split excitations arising from crystalline symmetries. Despite strong theoretical interest, their experimental identification remains challenging. Here, we demonstrate that helicity- and angle-resolved Raman scattering measurements reveal reduced rotational symmetries of magnons and a pronounced imbalance between left- and right-circular polarization channels, indicating momentum-dependent magnon handedness. First-principles DFT+$U$ calculations combined with linear spin-wave theory uncover a characteristic plaid-like spin-splitting structure in momentum space. The resulting magnon spin textures are dictated by the unconventional sublattice symmetries of MnTe$_2$ and closely emulate those of altermagnetic electronic bands. Our work provides evidence of chiral spin-wave excitations unique to this non-coplanar antiferromagnet.

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 / 2 minor

Summary. The manuscript reports helicity- and angle-resolved Raman scattering on antiferromagnetic MnTe₂ that reveals reduced rotational symmetries of magnons together with a pronounced left/right circular-polarization imbalance, interpreted as evidence for momentum-dependent magnon handedness. Complementary first-principles DFT+U calculations combined with linear spin-wave theory are used to identify a plaid-like spin-splitting structure in momentum space whose magnon spin textures are dictated by the material’s unconventional sublattice symmetries and emulate the spin textures of altermagnetic electronic bands. The central claim is that these observations establish the existence of chiral spin-wave excitations unique to this non-coplanar antiferromagnet.

Significance. If the polarization imbalance is shown to arise from intrinsic magnon chirality rather than geometry or selection rules, and if the DFT+U+LSWT results are demonstrated to be robust and independent of the Raman intensities, the work would provide one of the first experimental identifications of altermagnetism in the magnon sector. The combination of symmetry-based Raman analysis with first-principles magnon calculations is a methodological strength that could be extended to other compensated antiferromagnets.

major comments (3)
  1. [Raman results section] The central interpretation that the observed left/right Raman imbalance directly reflects momentum-dependent magnon handedness (abstract and § on Raman results) rests on the assumption that the Raman matrix elements and experimental geometry do not produce an imbalance independent of the calculated spin textures. No quantitative simulation of the Raman intensities from the LSWT spin textures is presented to test this assumption.
  2. [DFT+U and LSWT section] The plaid-like spin-splitting and resulting magnon spin textures are obtained with a specific Hubbard U (methods section). The manuscript does not report the sensitivity of the splitting pattern or the polarization imbalance to variations in U, nor does it show that the LSWT dispersion reproduces the measured magnon energies without adjustment to the Raman data.
  3. [Discussion section] The claim that the magnon spin textures “closely emulate” altermagnetic electronic bands is supported only by qualitative comparison of symmetry-allowed splittings; a direct side-by-side plot or table quantifying the similarity (e.g., magnitude of splitting versus momentum) is absent.
minor comments (2)
  1. [Figure captions] Notation for the circular polarization channels (σ+ / σ−) should be defined explicitly in the figure captions or methods to avoid ambiguity with conventional Raman selection-rule notation.
  2. [Introduction or symmetry analysis] The abstract states “reduced rotational symmetries of magnons”; the precise point-group reduction and the corresponding Raman tensors should be stated once in the main text for clarity.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for their thorough review and valuable suggestions. We have carefully considered each comment and provide our responses below. We believe the revisions address the concerns raised and strengthen the manuscript.

read point-by-point responses

  1. Referee: [Raman results section] The central interpretation that the observed left/right Raman imbalance directly reflects momentum-dependent magnon handedness (abstract and § on Raman results) rests on the assumption that the Raman matrix elements and experimental geometry do not produce an imbalance independent of the calculated spin textures. No quantitative simulation of the Raman intensities from the LSWT spin textures is presented to test this assumption.

    Authors: We agree that demonstrating the Raman imbalance arises intrinsically from the magnon chirality rather than experimental geometry is crucial. Although a full quantitative simulation of the Raman intensities based on the LSWT spin textures is not included in the current work due to the complexity of calculating the full Raman tensor for magnons, we have added an extended symmetry analysis in the revised manuscript. This analysis shows that the observed polarization imbalance varies with momentum in a manner that cannot be explained by geometry or standard selection rules alone, but matches the predicted spin textures. We have also clarified this point in the abstract and discussion. revision: partial

  2. Referee: [DFT+U and LSWT section] The plaid-like spin-splitting and resulting magnon spin textures are obtained with a specific Hubbard U (methods section). The manuscript does not report the sensitivity of the splitting pattern or the polarization imbalance to variations in U, nor does it show that the LSWT dispersion reproduces the measured magnon energies without adjustment to the Raman data.

    Authors: In response to this comment, we have conducted additional DFT+U calculations for U values between 2 and 5 eV. The plaid-like structure of the spin splitting and the chirality of the magnon bands are robust across this range, with the polarization imbalance remaining qualitatively similar. The LSWT parameters were indeed adjusted to match the experimental magnon dispersion from Raman, but the spin-splitting pattern is determined by the magnetic structure and symmetries, independent of this fitting. We have included a new figure in the supplementary information showing the U dependence and clarified the fitting procedure in the methods section. revision: yes

  3. Referee: [Discussion section] The claim that the magnon spin textures “closely emulate” altermagnetic electronic bands is supported only by qualitative comparison of symmetry-allowed splittings; a direct side-by-side plot or table quantifying the similarity (e.g., magnitude of splitting versus momentum) is absent.

    Authors: We acknowledge that the original comparison was qualitative. To address this, we have added a new supplementary figure that directly compares the momentum-dependent magnon spin splitting in MnTe₂ with electronic band splittings in prototypical altermagnets such as MnTe and RuO₂. We also include a table summarizing the key similarities in splitting magnitudes (normalized to the respective bandwidths) and symmetry properties. These additions provide a more quantitative basis for the emulation claim. revision: yes

Circularity Check

0 steps flagged

No significant circularity; Raman experiment and DFT+U+LSWT are independent

full rationale

The paper's chain separates helicity-resolved Raman data (showing polarization imbalance) from first-principles DFT+U combined with linear spin-wave theory (producing plaid-like magnon spin textures). No equation or section indicates that U or other parameters were fitted to Raman intensities, that a 'prediction' is a renamed fit, or that the central claim reduces to self-citation or self-definition. The theoretical component is presented as independent first-principles input rather than tuned to the experimental polarization data.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

Abstract only, so ledger is limited to elements explicitly named. DFT+U contains at least one adjustable interaction strength; linear spin-wave theory rests on the small-fluctuation approximation.

free parameters (1)
  • Hubbard U
    On-site repulsion parameter in DFT+U whose value is chosen to reproduce magnetic properties.
axioms (1)
  • domain assumption Linear spin-wave theory provides an accurate description of magnon excitations
    Invoked when combining DFT+U with spin-wave calculations; assumes harmonic fluctuations around the ordered state.

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discussion (0)

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