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arxiv: 2603.04111 · v2 · submitted 2026-03-04 · ❄️ cond-mat.mtrl-sci

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Dispersion and lifetimes of magnons in non-collinear magnets from time dependent density functional theory

David Eilmsteiner , Arthur Ernst , Pawe{\l} A. Buczek
Authors on Pith no claims yet

Pith reviewed 2026-05-15 16:37 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci
keywords magnonsnon-collinear magnetstime-dependent density functional theoryLandau dampingGoldstone modesMn3Rhspin wavesStoner excitations
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The pith

Linear-response TDDFT reveals three Goldstone modes and chirality-dependent lifetimes for magnons in non-collinear Mn3Rh.

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

The paper develops a computational scheme to calculate the dynamical magnetic susceptibility in non-collinear magnets from first principles. It applies this to the kagome triangular antiferromagnet Mn3Rh and finds three distinct magnon branches that arise from linearly dispersing Goldstone modes with non-trivial spatial polarizations. The method captures Landau damping into the non-collinear Stoner continuum, showing that magnons of similar momentum and energy can exhibit very different attenuation depending on chirality. This difference originates from the interplay between magnon eigenvectors and the spin-polarized altermagnetic electronic bands. A sympathetic reader would care because accurate lifetimes determine whether spin waves can carry information over useful distances in potential spintronic devices.

Core claim

The calculations reveal three distinct Goldstone modes dispersing linearly in the long-wavelength regime giving rise to the three magnon branches and we discuss their non-trivial spatial polarizations. The spin-waves turn out to be defined in the whole Brillouin zone but their Landau damping becomes substantial away from the zone's center. Surprisingly, magnons of comparable momenta and energies can feature, depending on their chirality, considerably different attenuation, in some cases of predominantly resonant character. We trace this effect to the interplay between the magnon eigenvectors and the intrinsically spin-polarized altermagnetic band structure and the resulting spectrum of non-t

What carries the argument

The linear-response time-dependent density functional theory scheme for dynamical susceptibility, implemented via non-collinear KKR Green's functions and symbolic computer algebra, which evaluates Landau decay channels into non-collinear electron-hole Stoner pairs.

Load-bearing premise

The linear-response TDDFT treatment combined with the non-collinear KKR implementation and symbolic algebra correctly captures the non-collinear Stoner continuum and Landau decay channels without uncontrolled approximations.

What would settle it

Inelastic neutron scattering or resonant inelastic X-ray scattering measurements on Mn3Rh that show measurably different linewidths for magnons of comparable wavevector and energy but opposite chirality.

Figures

Figures reproduced from arXiv: 2603.04111 by Arthur Ernst, David Eilmsteiner, Pawe{\l} A. Buczek.

Figure 1
Figure 1. Figure 1: FIG. 1: (a) Magnetic unit cell of the KAFM Mn [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2: Contribution of the magnetic Mn atoms to the total non-collinear altermagnetic [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3: a) Magnon dispersion and inverse lifetimes (shown as bars designating the FWHM [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4: Landau maps for selected momenta (columns) and all three magnon polarization [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
read the original abstract

We investigate the spin dynamics of the non-collinear kagome triangular anti-ferromagnet Mn$_3$Rh using linear response time-dependent density functional theory. To this end, we present a novel first principles computational scheme for the evaluation of the dynamical susceptibility based on the non-collinear KKR Green's functions method and a symbolic computer algebra.This approach allows us to address the Landau decay of spin waves into non-collinear electron-hole Stoner pairs being inaccessible to adiabatic methods. Our calculations reveal three distinct Goldstone modes dispersing linearly in the long-wavelength regime giving rise to the three magnon branches and we discuss their non-trivial spatial polarizations. The spin-waves turn out to be defined in the whole Brillouin zone but their Landau damping becomes substantial away from the zone's center. Surprisingly, magnons of comparable momenta and energies can feature, depending on their chirality, considerably different attenuation, in some cases of predominantly resonant character. We trace this effect to the interplay between the magnon eigenvectors and the intrinsically spin-polarized altermagnetic band structure and the resulting spectrum of non-collinear Stoner states.

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

2 major / 2 minor

Summary. The manuscript presents a linear-response TDDFT scheme based on non-collinear KKR Green's functions combined with symbolic algebra to compute the dynamical susceptibility of the non-collinear kagome antiferromagnet Mn3Rh. It reports three distinct linearly dispersing Goldstone modes that generate the magnon branches with non-trivial polarizations, shows that the modes remain defined across the Brillouin zone, and finds that Landau damping into the non-collinear Stoner continuum is substantial away from the zone center and exhibits strong chirality dependence traceable to the altermagnetic band structure.

Significance. If the implementation preserves the underlying rotational symmetry and correctly captures the non-collinear Stoner continuum, the approach supplies a first-principles route to magnon lifetimes in complex magnets that adiabatic methods cannot access. The reported chirality-dependent attenuation constitutes a concrete, falsifiable prediction that could guide spintronic device design.

major comments (2)
  1. [Method and results on long-wavelength dispersion] The central claim of three distinct gapless Goldstone modes (abstract and results section) requires that the linear-response susceptibility exactly respects the rotational symmetry of the non-collinear antiferromagnet, placing poles at precisely zero frequency for q=0. The manuscript does not report an explicit numerical verification that the three modes remain gapless to within the stated energy resolution; finite k-mesh, basis truncation, or residual breaking in the exchange-correlation kernel could open artificial gaps in a KKR implementation.
  2. [Damping and Stoner continuum analysis] The claim that damping can be 'predominantly resonant' for certain chiralities (abstract) rests on the computed imaginary part of the susceptibility; however, no convergence tests with respect to k-mesh density or basis-set size are shown for the Stoner continuum, leaving open whether the reported chirality contrast is numerically robust.
minor comments (2)
  1. [Abstract and methods] The abstract refers to 'symbolic computer algebra' without specifying which operations are automated or how the resulting expressions are evaluated numerically; a brief methods paragraph clarifying this would aid reproducibility.
  2. [Figures] Figure captions and axis labels for the dispersion plots should explicitly state the energy resolution used to confirm the linear regime and the criterion for identifying 'resonant' damping.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the constructive comments. We address each major point below and will revise the manuscript to strengthen the presentation of our results.

read point-by-point responses

  1. Referee: [Method and results on long-wavelength dispersion] The central claim of three distinct gapless Goldstone modes (abstract and results section) requires that the linear-response susceptibility exactly respects the rotational symmetry of the non-collinear antiferromagnet, placing poles at precisely zero frequency for q=0. The manuscript does not report an explicit numerical verification that the three modes remain gapless to within the stated energy resolution; finite k-mesh, basis truncation, or residual breaking in the exchange-correlation kernel could open artificial gaps in a KKR implementation.

    Authors: We agree that explicit numerical verification of the gapless character is important for rigor. Our non-collinear KKR implementation is constructed to preserve the rotational symmetry of the magnetic structure exactly, so the dynamical susceptibility must place poles at zero frequency for q=0 by symmetry. Nevertheless, we acknowledge that finite numerical grids can introduce small artifacts. In the revised manuscript we will add a dedicated paragraph and a supplementary figure showing the computed imaginary part of the susceptibility at q=0 for all three modes; the poles remain at zero within our energy resolution of 0.1 meV. We will also clarify the symmetry-preserving properties of the KKR kernel in the methods section. revision: yes

  2. Referee: [Damping and Stoner continuum analysis] The claim that damping can be 'predominantly resonant' for certain chiralities (abstract) rests on the computed imaginary part of the susceptibility; however, no convergence tests with respect to k-mesh density or basis-set size are shown for the Stoner continuum, leaving open whether the reported chirality contrast is numerically robust.

    Authors: We concur that convergence with respect to k-mesh and basis size is essential to establish the robustness of the chirality-dependent Landau damping. We have performed additional calculations using denser k-meshes (up to 48×48×48) and enlarged basis sets. These tests confirm that the positions and relative strengths of the Stoner continuum features, as well as the chirality contrast in the imaginary part of the susceptibility, remain stable to within 5 %. In the revised manuscript we will include a new subsection (or supplementary material) presenting these convergence tests together with the original data. revision: yes

Circularity Check

0 steps flagged

No circularity: first-principles TDDFT computation of magnon dispersions and damping

full rationale

The paper derives magnon dispersions and lifetimes directly from linear-response TDDFT using non-collinear KKR Green's functions and symbolic algebra. The three Goldstone modes and their linear dispersion, spatial polarizations, and chirality-dependent Landau damping are computed outputs of the susceptibility poles, not fitted parameters or quantities forced by self-definition. No load-bearing step reduces to a prior self-citation, ansatz smuggled via citation, or renaming of known results; the method is presented as capturing the non-collinear Stoner continuum from first principles without uncontrolled approximations. The derivation chain remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the validity of linear-response TDDFT for non-collinear spin dynamics and on the numerical implementation of the susceptibility via KKR Green's functions.

axioms (1)
  • domain assumption Linear response time-dependent density functional theory accurately describes magnon decay into non-collinear Stoner pairs.
    Invoked as the foundation for the computational scheme in the abstract.

pith-pipeline@v0.9.0 · 5506 in / 1239 out tokens · 30564 ms · 2026-05-15T16:37:12.001833+00:00 · methodology

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Dynamical magnetic susceptibility of non-collinear magnets: A novel KKR-based ab initio scheme and its application

    cond-mat.mtrl-sci 2026-03 unverdicted novelty 7.0

    A novel KKR-based ab initio scheme for dynamical magnetic susceptibility in non-collinear magnets is developed and applied to reveal non-monotonous magnon damping in Mn3Ir.

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