pith. machine review for the scientific record. sign in

arxiv: 2604.00412 · v2 · submitted 2026-04-01 · ❄️ cond-mat.mtrl-sci

Recognition: no theorem link

Robust d-wave altermagnetism in RbCr₂Se₂O

San-Dong Guo
Authors on Pith no claims yet

Pith reviewed 2026-05-13 22:47 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci
keywords altermagnetismd-wave altermagnetantiferromagnetismRbCr2Se2Opiezomagnetismdensity functional theorymagnetic configurationsstrain effect
0
0 comments X

The pith

RbCr2Se2O is a robust d-wave altermagnetic metal because its C-type and G-type magnetic states differ strongly in energy.

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

The paper predicts that the synthesized compound RbCr2Se2O forms a stable d-wave altermagnetic metal. Calculations show a large energy separation between its possible C-type and G-type antiferromagnetic orders. This separation holds steady when electron correlation strength and van der Waals corrections are varied. Related vanadium compounds show nearly equal energies for the same two orders, which creates experimental ambiguity about which state is realized. The work further finds that in-plane strain can produce a net magnetic moment in RbCr2Se2O through a direct piezomagnetic response, supplying a clear experimental signature for one of the two orders.

Core claim

RbCr2Se2O is a robust d-wave altermagnetic metal because the energy difference between C-type and G-type antiferromagnetic configurations is large and independent of electron correlation strength and van der Waals interaction. This large splitting distinguishes it from the nearly degenerate cases in KV2Se2O, Rb1-δV2Te2O and Cs1-δV2Te2O. Application of in-plane uniaxial strain generates a net total magnetic moment via the direct piezomagnetic effect, while the total moment remains zero for the G-type order. The same behavior is expected throughout the isostructural family XCr2Y2O (X = K, Rb, Cs; Y = S, Se, Te).

What carries the argument

Energy difference between C-type and G-type antiferromagnetic configurations obtained from density-functional calculations with varying Hubbard U and van der Waals corrections.

If this is right

  • A single magnetic ground state is selected for RbCr2Se2O, removing the assignment ambiguity seen in related compounds.
  • In-plane strain produces a net magnetization only for the C-type order, providing an experimental way to identify the realized state.
  • The d-wave altermagnetic character extends to the full family of XCr2Y2O materials without additional doping.
  • Metallic altermagnets in this structure can respond to strain with a net moment while remaining metallic.

Where Pith is reading between the lines

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

  • Strain control of net magnetism may extend to other metallic layered altermagnets without requiring carrier doping.
  • The family offers a platform to test how altermagnetic spin splitting affects transport or possible superconductivity.
  • Search for similar robust splitting in other transition-metal chalcogenide oxides with comparable layered motifs.

Load-bearing premise

Standard density-functional theory with common functionals and adjustable U correctly gives the true ground-state energy ordering in the real material.

What would settle it

Neutron diffraction or other direct probe that measures the actual magnetic order and energy scale in bulk RbCr2Se2O samples.

Figures

Figures reproduced from arXiv: 2604.00412 by San-Dong Guo.

Figure 1
Figure 1. Figure 1: FIG. 1. (Color online) For RbCr [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. (Color online) For RbCr [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. (Color online) For RbCr [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. (Color online) For RbCr [PITH_FULL_IMAGE:figures/full_fig_p003_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. (Color online) For KCr [PITH_FULL_IMAGE:figures/full_fig_p004_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. (Color online) For KCr [PITH_FULL_IMAGE:figures/full_fig_p005_6.png] view at source ↗
read the original abstract

The $\mathrm{KV_2Se_2O}$, $\mathrm{Rb_{1-\delta}V_2Te_2O}$ and $\mathrm{Cs_{1-\delta}V_2Te_2O}$ are experimentally confirmed to adopt either C-type or G-type antiferromagnetic configuration, corresponding to apparent or hidden altermagnetism. However, their nearly degenerate energies lead to inconsistent experimental assignments between the two antiferromagnetic configurations. Here, we predict that the experimentally synthesized $\mathrm{RbCr_2Se_2O}$ is a robust $d$-wave altermagnetic metal, since the energy difference between C-type and G-type configurations is large, which is independent of electron correlation strength and van der Waals interaction. Upon applying in-plane uniaxial strain, $\mathrm{RbCr_2Se_2O}$ can generate a net total magnetic moment via a direct piezomagnetic effect, which is distinct from semiconductor that typically requires carrier doping in addition to strain. This provides an experimental strategy for distinguishing the G-type antiferromagnetic configuration, in which the total magnetic moment remains zero under uniaxial strain. Our work presents an isostructural $d$-wave altermagnetic $\mathrm{RbCr_2Se_2O}$ analogous to $\mathrm{KV_2Se_2O}$, $\mathrm{Rb_{1-\delta}V_2Te_2O}$ and $\mathrm{Cs_{1-\delta}V_2Te_2O}$, which can facilitate further experimental verification. Furthermore, these results are universal across materials of this family $\mathrm{XCr_2Y_2O}$ (X=K, Rb, Cs; Y=S,Se, Te), thus expanding the family of altermagnets.

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 uses DFT+U calculations to predict that the experimentally synthesized RbCr₂Se₂O is a robust d-wave altermagnetic metal. It reports a large, sign-stable energy difference between C-type and G-type antiferromagnetic configurations that remains independent of Hubbard U (across a scanned range) and van der Waals corrections, in contrast to the near-degeneracy in related V-based compounds. The work further proposes that in-plane uniaxial strain induces a net magnetic moment via a direct piezomagnetic effect in this metal, providing an experimental route to distinguish the G-type order, and claims universality across the XCr₂Y₂O family.

Significance. If the reported energy ordering and its stability hold, the identification of RbCr₂Se₂O as a robust altermagnet expands the known family of d-wave altermagnets with a metallic example that does not require carrier doping for strain-induced magnetism. The direct total-energy comparisons and explicit checks versus U and vdW corrections constitute a reproducible computational result that can guide targeted experiments.

major comments (2)
  1. [DFT results section (energy difference vs U)] The central claim of robustness (large, U-independent energy difference between C-type and G-type orders) rests on total-energy comparisons whose physical relevance depends on the actual correlation strength in RbCr₂Se₂O. No linear-response or spectroscopic estimate of U for the Cr 3d states is provided, so the scanned U window may not bracket the material-specific value; this directly limits the strength of the 'independent of electron correlation strength' assertion.
  2. [Strain and piezomagnetism subsection] The piezomagnetic response under uniaxial strain is presented as a distinguishing feature for the metallic G-type state. However, the calculation assumes the strain-induced moment arises purely from the altermagnetic symmetry breaking without quantifying the magnitude relative to typical experimental resolution or comparing to possible competing mechanisms (e.g., weak ferromagnetism from spin-orbit effects).
minor comments (2)
  1. [Introduction and methods] Notation for the altermagnetic symmetry (d-wave) should be cross-referenced to the specific magnetic space group or irreducible representation used in the calculations.
  2. [Figure 2 or equivalent] Figure captions for the energy-vs-U plots should explicitly state the functional, k-point mesh, and convergence criteria to facilitate reproducibility.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments. We address each major comment below, indicating where revisions will be made to the manuscript.

read point-by-point responses

  1. Referee: [DFT results section (energy difference vs U)] The central claim of robustness (large, U-independent energy difference between C-type and G-type orders) rests on total-energy comparisons whose physical relevance depends on the actual correlation strength in RbCr₂Se₂O. No linear-response or spectroscopic estimate of U for the Cr 3d states is provided, so the scanned U window may not bracket the material-specific value; this directly limits the strength of the 'independent of electron correlation strength' assertion.

    Authors: We acknowledge that the manuscript does not provide a material-specific estimate of U via linear response or spectroscopy. Our calculations demonstrate that the energy difference between C-type and G-type configurations remains large and sign-stable across a wide scanned range of U (0–6 eV). In the revised manuscript we will qualify the claim by noting that this range encompasses typical literature values for Cr 3d electrons in related oxides and chalcogenides (commonly 2–5 eV), and we will add a brief discussion of how the ordering stability holds within physically plausible U values. This constitutes a partial revision that strengthens the presentation without overstating the result. revision: partial

  2. Referee: [Strain and piezomagnetism subsection] The piezomagnetic response under uniaxial strain is presented as a distinguishing feature for the metallic G-type state. However, the calculation assumes the strain-induced moment arises purely from the altermagnetic symmetry breaking without quantifying the magnitude relative to typical experimental resolution or comparing to possible competing mechanisms (e.g., weak ferromagnetism from spin-orbit effects).

    Authors: We agree that explicit quantification and comparison to competing effects would improve the subsection. Our DFT results show a strain-induced net moment of detectable size under modest uniaxial strain. In the revision we will report this magnitude explicitly and note that it lies well above typical experimental magnetization sensitivities. Regarding competing mechanisms such as SOC-induced weak ferromagnetism, our calculations are performed without SOC; the piezomagnetic response follows directly from the altermagnetic symmetry in the metallic G-type state. We will add a short discussion acknowledging that a full SOC comparison would require additional calculations, while emphasizing that the symmetry-allowed piezomagnetic channel is the dominant effect captured in the present work. revision: partial

Circularity Check

0 steps flagged

No significant circularity in DFT energy comparisons

full rationale

The paper's prediction rests on explicit total-energy calculations for C-type versus G-type AFM orders in RbCr2Se2O using standard DFT+U across a range of U values and with/without vdW corrections. These differences are obtained by solving the Kohn-Sham equations for the given structure and spin arrangements; they are not obtained by redefining any output quantity in terms of itself, fitting a parameter to a subset and relabeling a related output as a prediction, or invoking a self-citation chain that supplies the uniqueness or ansatz. The reported independence from U is shown by direct recomputation rather than by algebraic identity. The derivation therefore remains self-contained and does not reduce to its inputs by construction.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim rests on standard DFT total-energy comparisons whose accuracy for magnetic ordering is assumed rather than derived from first principles.

free parameters (1)
  • Hubbard U
    Electron correlation parameter varied over a range; claim asserts independence from its specific value.
axioms (1)
  • domain assumption Standard DFT functionals and pseudopotentials yield reliable relative energies between C-type and G-type AFM states in these layered compounds.
    Invoked implicitly when asserting robustness independent of correlation strength.

pith-pipeline@v0.9.0 · 5621 in / 1187 out tokens · 35096 ms · 2026-05-13T22:47:52.966666+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

39 extracted references · 39 canonical work pages · 1 internal anchor

  1. [1]

    ˘Smejkal, J

    L. ˘Smejkal, J. Sinova and T. Jungwirth, Beyond conven- tional ferromagnetism and antiferromagnetism: A phase with nonrelativistic spin and crystal rotation symmetry, Phys. Rev. X12, 031042 (2022)

    work page 2022

  2. [2]

    Mazin, Altermagnetism-a new punch line of fundamen- tal magnetism, Phys

    I. Mazin, Altermagnetism-a new punch line of fundamen- tal magnetism, Phys. Rev. X12, 040002 (2022)

    work page 2022

  3. [3]

    L. Bai, W. Feng, S. Liu, L. ˘Smejkal, Y. Mokrousov, and Y. Yao, Altermagnetism: Exploring New Frontiers in Magnetism and Spintronics, Adv. Funct. Mater. 2409327 (2024)

    work page 2024

  4. [4]

    H.-Y. Ma, M. L. Hu, N. N. Li, J. P. Liu, W. Yao, J. F. Jia and J. W. Liu, Multifunctional antiferromagnetic ma- terials with giant piezomagnetism and noncollinear spin current, Nat. Commun.12, 2846 (2021)

    work page 2021

  5. [5]

    Y. Liu, J. Yu and C. C. Liu, Twisted Magnetic Van der Waals Bilayers: An Ideal Platform for Altermagnetism, Phys. Rev. Lett.133, 206702 (2024)

    work page 2024

  6. [6]

    X. Chen, D. Wang, L. Y. Li and B. Sanyal, Giant spin- splitting and tunable spin-momentum locked transport in room temperature collinear antiferromagnetic semimetal- lic CrO monolayer, Appl. Phys. Lett.123, 022402 (2023)

    work page 2023

  7. [7]

    B. Pan, P. Zhou, P. Lyu, H. Xiao, X. Yang, and L. Sun, General stacking theory for altermagnetism in bi- layer systems, Phys. Rev. Lett.133, 166701 (2024)

    work page 2024

  8. [8]

    H. Bai, L. Han, X. Y. Feng, Y. J. Zhou, R. X. Su, Q. Wang, L. Y. Liao, W. X. Zhu, X. Z. Chen, F. Pan, X. L. Fan, and C. Song, Observation of spin splitting torque in 6 a collinear antiferromagnet RuO 2, Phys. Rev. Lett.128, 197202 (2022)

    work page 2022

  9. [9]

    S. Lee, S. Lee, S. Jung, J. Jung, D. Kim, Y. Lee, B. Seok, J. Kim, B. G. Park, L. Smejkal, C. J. Kang, and C. Kim, Broken Kramers degeneracy in altermagnetic MnTe, Phys. Rev. Lett.132, 036702 (2024)

    work page 2024

  10. [10]

    G. Yang, Z. Li, S. Yang, J. Li, H. Zheng, W. Zhu, Z. Pan, Y. Xu, S. Cao, W. Zhao, A. Jana, J. Zhang, M. Ye, Y. Song, L. H. Hu, L. Yang, J. Fujii, I. Vobornik, M. Shi, H. Yuan, Y. Zhang, Y. Xu, and Y. Liu, Three-dimensional mapping of the altermagnetic spin splitting in CrSb, Nat Commun16, 1442 (2025)

    work page 2025

  11. [11]

    Z. Zhou, X. Cheng, M. Hu, R. Chu, H. Bai, L. Han, J. Liu, F. Pan and C. Song, Manipulation of the altermag- netic order in CrSb via crystal symmetry, Nature638, 645 (2025)

    work page 2025

  12. [12]

    J. Ding, Z. Jiang, X. Chen, Z. Tao, Z. Liu, T. Li, J. Liu, J. Sun and J. Cheng, Large Band Splitting ing-Wave Altermagnet CrSb, Phys. Rev. Lett.133, 206401 (2024)

    work page 2024

  13. [13]

    Jiang, M

    B. Jiang, M. Hu, J. Bai, Z. Song, C. Mu, G. Qu, W. Li, W. Zhu, H. Pi, Z. Wei, Y. J. Sun, Y. Huang, X. Zheng, Y. Peng, L. He, S. Li, J. Luo, Z. Li, G. Chen, H. Li, H. Weng and T. Qian, A metallic room-temperature d-wave altermagnet, Nat. Phys.21, 754 (2025)

    work page 2025

  14. [14]

    F. Zhang X. Cheng, Z. Yin, C. Liu, L. Deng, Y. Qiao, Z. Shi, S. Zhang, J. Lin, Z. Liu, M. Ye, Y. Huang, X. Meng, C. Zhang, T. Okuda, K. Shimada, S. Cui, Y. Zhao, G.- H. Cao, S. Qiao, J. Liu and C. Chen, Crystal-symmetry- paired spin-valley locking in a layered room-temperature metallic altermagnet candidate, Nature Phys.21, 760 (2025)

    work page 2025

  15. [15]

    G. Yang, R. Chen, C. Liu et al., Observation of hid- den altermagnetism in Cs 1−δV2Te2O, arXiv:2512.00972 (2025)

    work page internal anchor Pith review Pith/arXiv arXiv 2025

  16. [16]

    C.-C. Liu, J. Li, J.-Y. Liu, J.-Y. Lu, H.-X. Li, Y. Liu and G.-H. Cao, Physical properties and first-principles calculations of an altermagnet candidate Cs 1−δV2Te2O, Phys. Rev. B112, 224439 (2025)

    work page 2025

  17. [17]

    Y. Sun, Y. Huang, J. Cheng et al., Antiferromagnetic structure of KV 2Se2O: A neutron diffraction study, Phys. Rev. B112, 184416 (2025)

    work page 2025

  18. [18]

    Xiong, X

    J.-X. Xiong, X. Zhang, L.-D. Yuan and A. Zunger, Mat- ter with apparent and hidden spin physics, Matter doi: 10.1016/j.matt.2026.102674 (2026)

    work page doi:10.1016/j.matt.2026.102674 2026

  19. [19]

    S. Guan, J. X. Xiong, Z. Wang, and J. W. Luo, Progress of hidden spin polarization in inversion-symmetric crys- tals, Sci. China-Phys. Mech. Astron.65, 237301 (2022)

    work page 2022

  20. [20]

    L. D. Yuan, X. Zhang, C. M. Acosta and A. Zunger, Uncovering spin-orbit coupling-independent hidden spin polarization of energy bands in antiferromagnets, Nat. Commun.14, 5301 (2023)

    work page 2023

  21. [21]

    S. D. Guo and P. Zhou, Hidden half-metallicity, arXiv:2601.07128 (2026)

    work page arXiv 2026

  22. [22]

    S. D. Guo, Hidden altermagnetism, Front. Phys.21, 025201 (2026); arXiv:2411.13795 (2024)

    work page arXiv 2026

  23. [23]

    S. D. Guo, Hidden fully-compensated ferrimagnetism, Phys. Chem. Chem. Phys.28, 2188 (2026)

    work page 2026

  24. [24]

    Matsuda, H

    J. Matsuda, H. Watanabe and R. Arita, Multiferroic Collinear Antiferromagnets with Hidden Altermagnetic Spin Splitting, Phys. Rev. Lett.134, 226703 (2025)

    work page 2025

  25. [25]

    Zhang, L

    T. Zhang, L. Yuan, J. M. Rondinelli, H. A. Fertig and S. Zhang, Tunable Hidden Altermagnetic Spin Splitting in Layered RuddlesdenCPopper Oxides, Nano Lett.26, 2778 (2026)

    work page 2026

  26. [26]

    Q. N. Meier, A. Carta, C. Ederer and A. Cano, Net and Compensated Altermagnetism from Staggered Orbital Order: Layer-Dependent Spin Splitting in Srn+1CrnO3n+1, Phys. Rev. Lett.136, 116705 (2026)

    work page 2026

  27. [27]

    I.arXiv preprint arXiv:2602.186722026

    B. Thapa, P.-H. Chang, K. Belashchenko and I. I. Mazin, Is altermagnetism in vanadium oxychalcogenides a lost cause?, arXiv:2602.18672 (2026)

    work page arXiv 2026

  28. [28]

    S. D. Guo and Y. Liu, Distinguishing apparent and hid- den altermagnetism via uniaxial strain in CsV 2Te2O- family, arXiv:2603.25136 (2026)

    work page arXiv 2026

  29. [29]

    R. Xu, Y. Gao and J. Liu, Chemical design of monolayer altermagnets, Natl. Sci. Rev.13, nwaf528 (2026)

    work page 2026

  30. [30]

    X. Sun, P. Chen, X. Wen and H. Chen, Synthesis, Struc- ture, and Physical Properties of RbCr 2Se2O, Crystals 16, 56 (2026)

    work page 2026

  31. [31]

    Hohenberg and W

    P. Hohenberg and W. Kohn, Inhomogeneous Electron Gas, Phys. Rev.136, B864 (1964)

    work page 1964

  32. [32]

    Kohn and L

    W. Kohn and L. J. Sham, Self-Consistent Equations In- cluding Exchange and Correlation Effects, Phys. Rev. 140, A1133 (1965)

    work page 1965

  33. [33]

    Kresse, Ab initio molecular dynamics for liquid met- als, J

    G. Kresse, Ab initio molecular dynamics for liquid met- als, J. Non-Cryst. Solids193, 222 (1995)

    work page 1995

  34. [34]

    Kresse and J

    G. Kresse and J. Furthm¨uller, Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set, Comput. Mater. Sci. 6,15(1996)

    work page 1996

  35. [35]

    Kresse and D

    G. Kresse and D. Joubert, From ultrasoft pseudopoten- tials to the projector augmented-wave method, Phys. Rev. B59, 1758 (1999)

    work page 1999

  36. [36]

    J. P. Perdew, K. Burke and M. Ernzerhof, Generalized gradient approximation made simple, Phys. Rev. Lett. 77, 3865 (1996)

    work page 1996

  37. [37]

    S. L. Dudarev, G. A. Botton, S. Y. Savrasov, C. J. Humphreys, and A. P. Sutton, Electron-energy-loss spec- tra and the structural stability of nickel oxide: An LSDA+U study, Phys. Rev. B57, 1505 (1998)

    work page 1998

  38. [38]

    Grimme, S

    S. Grimme, S. Ehrlich and L. Goerigk, Effect of the damping function in dispersion corrected density func- tional theory, J. Comput. Chem.32, 1456 (2011)

    work page 2011

  39. [39]

    See Supplemental Material at [] for the associated energy differences of magnetic configurations, band structures and lattice parameters

    work page