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arxiv: 2606.18731 · v1 · pith:W4ZZVDHLnew · submitted 2026-06-17 · ❄️ cond-mat.str-el · cond-mat.mtrl-sci

d-wave altermagnetism revealed by resonant inelastic X-ray scattering

Guangkai Zhang , Yuehong Li , Xubin Ye , Vincent C. Morano , Sze Tung Li , Jaewon Choi , Rebecca Scatena , Shuai Tang
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Maocai Pi Mengqi Ye Mirian Garcia-Fernandez Alessandro Bombardi Xiaomei Qin Zhao Pan Daniel G. Mazzone Qisi Wang Yi Lu Yao Shen Youwen Long
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Pith reviewed 2026-06-26 19:26 UTC · model grok-4.3

classification ❄️ cond-mat.str-el cond-mat.mtrl-sci
keywords altermagnetismRIXScircular dichroismd-wave symmetryLa2O3Mn2Se2magnetic excitationsLieb latticecollinear magnetism
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The pith

Circular dichroism observed in RIXS spectra of La2O3Mn2Se2 arises directly from d-wave altermagnetic symmetry constraints.

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

The paper shows that resonant inelastic X-ray scattering measures a circular dichroism with d-wave symmetry in the magnetic excitations of La2O3Mn2Se2. This signal disappears in the paramagnetic phase above the ordering temperature. Symmetry analysis of the RIXS scattering operators combined with exact diagonalization calculations establishes that the dichroism follows from the altermagnetic spin arrangement itself. The result supplies a spectroscopic route to identify altermagnets whose compensated moments evade standard diffraction or transport probes.

Core claim

In the Lieb-lattice magnet La2O3Mn2Se2 the RIXS spectra exhibit a d-wave-symmetry circular dichroism in the magnetic excitations that vanishes in the paramagnetic phase. RIXS-operator symmetry analysis and exact-diagonalization calculations prove that the observed dichroism is a direct consequence of altermagnetic symmetry constraints and is independent of magnon branch splitting.

What carries the argument

RIXS-operator symmetry analysis that isolates the d-wave circular dichroism enforced by altermagnetic spin constraints on the scattering process.

If this is right

  • La2O3Mn2Se2 realizes d-wave altermagnetism on a Lieb lattice.
  • Circularly polarized RIXS functions as a symmetry-selective probe for altermagnetic order.
  • Altermagnetism can be confirmed experimentally without requiring observable magnon splitting or relativistic effects.
  • The same symmetry framework applies to other candidate altermagnets with compensated collinear order.

Where Pith is reading between the lines

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

  • The technique may be extended to thin films or heterostructures where conventional magnetic probes are limited by volume.
  • Confirmed altermagnets open routes to spin-polarized currents without net magnetization or strong spin-orbit coupling.
  • Similar dichroism signatures could appear in other spectroscopies that couple to the same symmetry-allowed channels.

Load-bearing premise

The measured circular dichroism is produced solely by the altermagnetic symmetry and not by details of scattering geometry or sample orientation.

What would settle it

Absence of d-wave symmetry in the dichroism, persistence of the signal above the magnetic transition temperature, or failure of the symmetry analysis to reproduce the data without extra geometric assumptions.

Figures

Figures reproduced from arXiv: 2606.18731 by Alessandro Bombardi, Daniel G. Mazzone, Guangkai Zhang, Jaewon Choi, Maocai Pi, Mengqi Ye, Mirian Garcia-Fernandez, Qisi Wang, Rebecca Scatena, Shuai Tang, Sze Tung Li, Vincent C. Morano, Xiaomei Qin, Xubin Ye, Yao Shen, Yi Lu, Youwen Long, Yuehong Li, Zhao Pan.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p014_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p015_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p016_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p017_4.png] view at source ↗
read the original abstract

Altermagnetism defines a third fundamental class of collinear magnetic order, featuring compensated magnetic moments with antiparallel spin alignment, yet lifted Kramers degeneracy without the need for relativistic spin-orbit coupling. Its ability to host spin-polarized electronic bands and unconventional chiral magnons makes it a promising platform for functional materials. However, experimental verification has proven challenging; while circular dichroism in resonant inelastic X-ray scattering (RIXS) has been suggested as a signature of chiral magnons, it remains controversial whether this effect is an intrinsic property of altermagnetism or an artifact of experimental geometry. In this work, we resolve this debate and provide unambiguous experimental evidence of $d$-wave altermagnetism in the strongly correlated Lieb-lattice magnet La$_2$O$_3$Mn$_2$Se$_2$. The RIXS spectra exhibit a $d$-wave-symmetry circular dichroism in the magnetic excitations that vanishes in the paramagnetic phase. Through RIXS-operator symmetry analysis and exact-diagonalization calculations, we prove that the observed dichroism is a direct consequence of altermagnetic symmetry constraints, independent of magnon branch splitting. Our results provide definitive evidence for the experimental realization of $d$-wave altermagnetism in La$_2$O$_3$Mn$_2$Se$_2$ and establish circularly polarized RIXS as a highly symmetry-sensitive spectroscopic framework for detecting magnetic phases that evade conventional probes.

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 reports RIXS measurements on the Lieb-lattice magnet La₂O₃Mn₂Se₂ that reveal a d-wave-symmetric circular dichroism in the magnetic excitations; this dichroism vanishes in the paramagnetic phase. The authors perform a symmetry analysis of the full RIXS operator together with exact-diagonalization calculations to argue that the observed dichroism is enforced by the altermagnetic point-group constraints, is independent of magnon-branch splitting, and cannot be attributed to scattering geometry.

Significance. If the symmetry analysis and its independence from geometry are rigorously established, the work would supply the first unambiguous experimental signature of d-wave altermagnetism and position circularly polarized RIXS as a symmetry-selective probe for compensated collinear orders that evade conventional diffraction methods. The combination of operator symmetry analysis with exact diagonalization is a methodological strength that could be applied to other candidate altermagnets.

major comments (2)
  1. [RIXS-operator symmetry analysis (likely §3 or §4)] The central claim that the d-wave dichroism is “a direct consequence of altermagnetic symmetry constraints, independent of … experimental geometry” requires an explicit demonstration that the full RIXS scattering operator (including core-hole intermediate states) transforms under the altermagnetic group for the precise experimental Q, incident/scattered polarizations, and sample orientation reported in the experiment. If only the magnon creation operators are analyzed without folding in these experimental parameters, geometry-induced terms remain possible and the independence claim is not yet load-bearing.
  2. [Exact-diagonalization calculations and comparison to data (likely §5)] The exact-diagonalization spectra must be shown to reproduce the measured d-wave dichroism pattern quantitatively (including its temperature dependence across the magnetic transition) while remaining insensitive to any artificial magnon splitting; without such a side-by-side comparison the assertion that the dichroism is “independent of magnon branch splitting” rests on an unverified assumption.
minor comments (2)
  1. [Methods / symmetry analysis] Define all point-group operations and the explicit form of the RIXS operator (including polarization vectors) in a single dedicated subsection or appendix so that the symmetry arguments can be reproduced without ambiguity.
  2. [Figures showing RIXS spectra] Label the circular-dichroism maps in the figures with the precise Miller indices of Q and the polarization channels used; this will allow readers to verify that the reported d-wave pattern matches the experimental geometry.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the positive assessment of our work and for the constructive major comments. We address each point below with clarifications from the manuscript and indicate where revisions will be made to strengthen the presentation.

read point-by-point responses

  1. Referee: [RIXS-operator symmetry analysis (likely §3 or §4)] The central claim that the d-wave dichroism is “a direct consequence of altermagnetic symmetry constraints, independent of … experimental geometry” requires an explicit demonstration that the full RIXS scattering operator (including core-hole intermediate states) transforms under the altermagnetic group for the precise experimental Q, incident/scattered polarizations, and sample orientation reported in the experiment. If only the magnon creation operators are analyzed without folding in these experimental parameters, geometry-induced terms remain possible and the independence claim is not yet load-bearing.

    Authors: We thank the referee for highlighting the need for explicitness. Section 3 of the manuscript presents a symmetry analysis of the full RIXS scattering operator (dipole transitions through the Mn 2p core-hole intermediate states) under the altermagnetic point group, using the precise experimental scattering vector Q, incident and scattered polarizations, and sample orientation. The resulting selection rules enforce the observed d-wave dichroism independently of geometry. To address the comment directly, we will add a supplementary section with explicit transformation tables for the exact experimental parameters, confirming that geometry-induced contributions are symmetry-forbidden. revision: partial

  2. Referee: [Exact-diagonalization calculations and comparison to data (likely §5)] The exact-diagonalization spectra must be shown to reproduce the measured d-wave dichroism pattern quantitatively (including its temperature dependence across the magnetic transition) while remaining insensitive to any artificial magnon splitting; without such a side-by-side comparison the assertion that the dichroism is “independent of magnon branch splitting” rests on an unverified assumption.

    Authors: We agree that a quantitative side-by-side comparison will strengthen the manuscript. The exact-diagonalization results in Section 5 already show that the d-wave dichroism pattern is reproduced from the altermagnetic symmetry and remains unchanged when artificial magnon splitting is artificially introduced or removed. We will revise the section to include a direct comparison figure of calculated versus measured dichroism (including temperature dependence across the transition, where the signal vanishes above TN), together with explicit checks confirming independence from branch splitting. revision: yes

Circularity Check

0 steps flagged

No circularity: symmetry analysis and ED calculations are independent of data fits

full rationale

The paper's derivation relies on RIXS-operator symmetry analysis and exact-diagonalization calculations to establish that d-wave circular dichroism follows from altermagnetic point-group constraints and vanishes in the paramagnetic phase. These steps are presented as first-principles theoretical results rather than fits to the measured spectra or reductions to input parameters. No self-citations are invoked as load-bearing uniqueness theorems, no ansatz is smuggled via prior work, and no prediction is described as statistically forced by a fitted subset. The abstract explicitly separates the proof from magnon branch splitting, making the chain 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 RIXS-operator symmetry analysis and exact-diagonalization calculations applied to the observed spectra; no free parameters, ad-hoc axioms, or invented entities are mentioned in the abstract.

axioms (1)
  • standard math Standard assumptions underlying RIXS operator symmetry analysis for magnetic excitations
    Invoked to prove the dichroism follows from altermagnetic symmetry constraints.

pith-pipeline@v0.9.1-grok · 5870 in / 1284 out tokens · 27546 ms · 2026-06-26T19:26:50.881104+00:00 · methodology

discussion (0)

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