pith. sign in

arxiv: 2510.00509 · v2 · pith:PFJG7BSWnew · submitted 2025-10-01 · ❄️ cond-mat.mtrl-sci

Orbital Altermagnetism

Pith reviewed 2026-05-22 12:14 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci
keywords orbital altermagnetismaltermagnetismorbital magnetismloop currentssquare-kagome latticemagnetotransportfirst-principles calculations2D ferromagnets
0
0 comments X

The pith

Orbital altermagnetism is a symmetry-protected order of pure orbital magnetic moments that produces d-wave-like orbital-momentum locking.

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

The paper establishes that orbital altermagnetism exists as a magnetic order based solely on orbital degrees of freedom. It features anti-parallel orbital magnetic moments in real space paired with momentum-dependent splittings in the electronic bands. This order originates from staggered loop currents, demonstrated through a minimal tight-binding model on a square-kagome lattice with complex hoppings. First-principles results indicate the orbital order appears independently of spin ordering in in-plane ferromagnets such as CuBr2 and VS2. This separation allows unambiguous experimental detection and supports applications in orbital-based transport and spintronics.

Core claim

Orbital altermagnetism is characterized by ordered anti-parallel orbital magnetic moments in real space but momentum-dependent orbital band splittings, analogous to spin altermagnetism. Using a minimal tight-binding model with complex hoppings in a square-kagome lattice, such order inherently arises from staggered loop currents, producing a d-wave-like orbital-momentum locking. First-principles calculations show that orbital altermagnetism emerges independent of spin ordering in in-plane ferromagnets of CuBr2 and VS2, so that it can be unambiguously identified experimentally. It may also coexist with spin altermagnetism, such as in monolayer MoO and CrO.

What carries the argument

Symmetry-protected magnetic order of pure orbital degrees of freedom with anti-parallel orbital moments and momentum-dependent band splittings arising from staggered loop currents.

If this is right

  • Orbital altermagnetism can be unambiguously identified experimentally in CuBr2 and VS2 because it appears independent of spin ordering.
  • It may coexist with spin altermagnetism in materials such as monolayer MoO and CrO.
  • It offers an alternative platform for symmetry-driven magnetotransport.
  • It supports orbital-based spintronics through effects like large nonlinear current-induced orbital magnetization.

Where Pith is reading between the lines

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

  • Angle-resolved photoemission could map the momentum-dependent orbital splittings directly in these materials.
  • Devices might exploit orbital currents for information processing without requiring spin manipulation.
  • The concept could extend to other lattice geometries or higher-dimensional structures for broader material searches.

Load-bearing premise

First-principles calculations can isolate pure orbital magnetic moments and band splittings without significant contamination from spin-orbit coupling or other relativistic effects.

What would settle it

An experiment measuring orbital band splittings or magnetic moments in CuBr2 or VS2 that shows the orbital order vanishes when spin ordering is independently suppressed.

Figures

Figures reproduced from arXiv: 2510.00509 by Feng Liu, Huaqing Huang, Mingxiang Pan.

Figure 1
Figure 1. Figure 1: FIG. 1. (a) Unit cell (dashed box) of the tight-binding model described by Eq. ( [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. (a) Top and side views of the monolayer CuBr [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. (a) Top and side views of the monolayer MoO lattice. Green arrows indicate the spin magnetic moments on Mo atoms. [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. A schematic diagram illustrates how an in-plane ferromagnet can be used to achieve an out-of-plane orbital antiferro [PITH_FULL_IMAGE:figures/full_fig_p013_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. (a) [PITH_FULL_IMAGE:figures/full_fig_p014_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. (a) Side view of the lattice structure (red O atoms, blue Cr atoms). (b) Band structures of CrO, where the color [PITH_FULL_IMAGE:figures/full_fig_p015_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. (a) Crystal structure of monolayer VS [PITH_FULL_IMAGE:figures/full_fig_p015_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: shows the calculated band structure of CuBr2 together with the corresponding Lz distribution in momen￾tum space for the configuration with spin polarization along the x-axis [PITH_FULL_IMAGE:figures/full_fig_p016_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9 [PITH_FULL_IMAGE:figures/full_fig_p016_9.png] view at source ↗
read the original abstract

We introduce the concept of \emph{orbital altermagnetism}, a symmetry-protected magnetic order of pure orbital degrees of freedom. It is characterized with ordered anti-parallel orbital magnetic moments in real space but momentum-dependent orbital band splittings, analogous to spin altermagnetism. Using a minimal tight-binding model with complex hoppings in a square-kagome lattice, we show that such order inherently arises from staggered loop currents, producing a $d$-wave-like orbital-momentum locking. First-principles calculations show that orbital altermagnetism emerges independent of spin ordering in in-plane ferromagnets of CuBr$_2$ and VS$_2$, so that it can be unambiguously identified experimentally. On the other hand, it may also coexist with spin altermagnetism, such as in monolayer MoO and CrO. The orbital altermagnetism offers an alternative platform for symmetry-driven magnetotransport and orbital-based spintronics, as exemplified by large nonlinear current-induced orbital magnetization.

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

1 major / 2 minor

Summary. The paper introduces orbital altermagnetism as a symmetry-protected order of pure orbital magnetic moments, featuring anti-parallel moments in real space and d-wave-like orbital band splittings in momentum space. It constructs a minimal tight-binding model on the square-kagome lattice with complex hoppings arising from staggered loop currents to demonstrate the orbital-momentum locking, and presents first-principles calculations showing this order in in-plane ferromagnets CuBr2 and VS2 independent of spin ordering, as well as coexistence with spin altermagnetism in monolayer MoO and CrO. The work highlights potential for symmetry-driven magnetotransport and orbital spintronics through nonlinear current-induced orbital magnetization.

Significance. If the results hold, the introduction of orbital altermagnetism provides a distinct platform for orbital-based electronics and transport phenomena that can be decoupled from spin ordering. The tight-binding model supplies a transparent microscopic mechanism grounded in loop currents, and the material-specific DFT examples (CuBr2, VS2, MoO, CrO) offer concrete candidates for experimental verification and applications.

major comments (1)
  1. [First-principles calculations for CuBr2 and VS2] The central claim that orbital altermagnetism appears independent of spin ordering in CuBr2 and VS2 (and can therefore be unambiguously identified experimentally) is load-bearing for the strongest result. The first-principles section does not explicitly demonstrate that the reported orbital moments and band splittings survive in non-spin-polarized calculations or in runs with spin polarization constrained to zero; standard DFT+SOC workflows couple the channels, so the separation must be shown to secure the independence assertion.
minor comments (2)
  1. [Abstract] The abstract states that DFT is used but omits convergence parameters, k-point sampling, or the precise protocol for extracting orbital moments versus spin contributions; adding these details would improve reproducibility.
  2. [Tight-binding model] In the tight-binding model section, the explicit form of the complex hopping terms and the relation to staggered loop currents could be stated more formally (e.g., via an equation for the phase factors) to make the d-wave locking derivation fully transparent.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful and constructive review of our manuscript on orbital altermagnetism. We appreciate the recognition of the potential significance of the concept and the value of the tight-binding model and material examples. We address the major comment below and will revise the manuscript to strengthen the presentation of the first-principles results.

read point-by-point responses
  1. Referee: [First-principles calculations for CuBr2 and VS2] The central claim that orbital altermagnetism appears independent of spin ordering in CuBr2 and VS2 (and can therefore be unambiguously identified experimentally) is load-bearing for the strongest result. The first-principles section does not explicitly demonstrate that the reported orbital moments and band splittings survive in non-spin-polarized calculations or in runs with spin polarization constrained to zero; standard DFT+SOC workflows couple the channels, so the separation must be shown to secure the independence assertion.

    Authors: We agree that an explicit demonstration of orbital altermagnetism in the absence of spin polarization is necessary to fully substantiate the independence claim. In the revised manuscript we will add non-spin-polarized DFT+SOC calculations for CuBr₂ and VS₂, together with additional runs in which spin moments are constrained to zero. These calculations will show that the orbital magnetic moments and the associated d-wave-like band splittings remain essentially unchanged, confirming that the orbital order is not induced by the spin channel. The first-principles section and associated figures will be updated to include these results and to clarify the computational protocol. revision: yes

Circularity Check

0 steps flagged

No significant circularity; derivation relies on explicit model construction and first-principles results

full rationale

The paper introduces orbital altermagnetism as a new concept and demonstrates its emergence via a minimal tight-binding model on a square-kagome lattice (with complex hoppings producing staggered loop currents and d-wave orbital-momentum locking) plus separate first-principles calculations on CuBr2 and VS2. These steps do not reduce the reported orbital moments or band splittings to parameters defined by the target phenomenon itself, nor do they rename known results, smuggle ansatze via self-citation, or treat fitted inputs as predictions. The independence claim rests on explicit computational protocols rather than self-referential definitions, making the chain self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 1 invented entities

The work relies on standard tight-binding assumptions and DFT approximations common to the field; no new free parameters are explicitly fitted in the abstract, and the orbital order is derived from symmetry and staggered currents rather than ad-hoc entities.

axioms (2)
  • domain assumption Complex hoppings in the square-kagome lattice produce staggered loop currents that generate orbital magnetic moments.
    Invoked in the minimal model section to link real-space order to momentum-space splittings.
  • domain assumption First-principles calculations can separate orbital contributions from spin ordering in the chosen in-plane ferromagnets.
    Central to the claim of independent identification in CuBr2 and VS2.
invented entities (1)
  • orbital altermagnetism no independent evidence
    purpose: To name and classify the proposed symmetry-protected orbital magnetic order analogous to spin altermagnetism.
    The central new concept introduced; no independent experimental signature is provided beyond the model and DFT predictions.

pith-pipeline@v0.9.0 · 5696 in / 1452 out tokens · 38404 ms · 2026-05-22T12:14:42.261494+00:00 · methodology

discussion (0)

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

Forward citations

Cited by 3 Pith papers

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

  1. Topological piezomagnetic effect in two-dimensional Dirac quadrupole altermagnets

    cond-mat.str-el 2026-02 unverdicted novelty 7.0

    Dirac quadrupole altermagnets in 2D exhibit a topological orbital piezomagnetic effect from strain altering their quadrupole Dirac points.

  2. $P$-wave Orbital Magnetism

    cond-mat.mes-hall 2026-04 unverdicted novelty 6.0

    P-wave orbital magnetism protected by combined translation and time-reversal symmetry is proposed to originate from loop-current-induced orbital textures in a 2D Dirac lattice model, measurable via orbital Hall conductivity.

  3. Topologically non-trivial gap function and topology-induced time-reversal symmetry breaking in a superconductor with singular dynamical interaction

    cond-mat.str-el 2026-04 unverdicted novelty 5.0

    A repulsive Hubbard term selects topologically nontrivial pairing over the trivial one in singular-interaction superconductors, with the transition passing through a topology-induced time-reversal symmetry breaking phase.

Reference graph

Works this paper leans on

117 extracted references · 117 canonical work pages · cited by 3 Pith papers

  1. [1]

    ˇSmejkal, J

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

  2. [2]

    ˇSmejkal, J

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

  3. [3]

    ˇSmejkal, R

    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)

  4. [4]

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

  5. [5]

    C. Song, H. Bai, Z. Zhou, L. Han, H. Reichlova, J. H. Dil, J. Liu, X. Chen, and F. Pan, Altermagnets as a new class of functional materials, Nat. Rev. Mater.10, 473 (2025)

  6. [6]

    L. Bai, W. Feng, S. Liu, L. ˇSmejkal, Y. Mokrousov, and Y. Yao, Altermagnetism: Exploring new frontiers in magnetism and spintronics, Adv. Funct. Mater.34, 2409327 (2024)

  7. [7]

    ˇSmejkal, A

    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)

  8. [9]

    Gonz´ alez-Hern´ andez, L.ˇSmejkal, K

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

  9. [10]

    A. Bose, N. J. Schreiber, R. Jain, D.-F. Shao, H. P. Nair, J. Sun, X. S. Zhang, D. A. Muller, E. Y. Tsymbal, D. G. Schlom, and D. C. Ralph, Tilted spin current generated by the collinear antiferromagnet ruthenium dioxide, Nat. Electron.5, 267 (2022)

  10. [11]

    H. Bai, Y. C. Zhang, Y. J. Zhou, P. Chen, C. H. Wan, L. Han, W. X. Zhu, S. X. Liang, Y. C. Su, X. F. Han, F. Pan, and C. Song, Efficient spin-to-charge conversion via altermagnetic spin splitting effect in antiferromagnet ruo2, Phys. Rev. Lett.130, 216701 (2023)

  11. [12]

    Y. Fang, J. Cano, and S. A. A. Ghorashi, Quantum geometry induced nonlinear transport in altermagnets, Phys. Rev. Lett.133, 106701 (2024)

  12. [13]

    Ezawa, Third-order and fifth-order nonlinear spin- current generation ing-wave andi-wave altermagnets and perfectly nonreciprocal spin current inf-wave mag- nets, Phys

    M. Ezawa, Third-order and fifth-order nonlinear spin- current generation ing-wave andi-wave altermagnets and perfectly nonreciprocal spin current inf-wave mag- nets, Phys. Rev. B111, 125420 (2025)

  13. [14]

    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)

  14. [15]

    Tanaka, T

    K. Tanaka, T. Nomoto, and R. Arita, Approaches to tunnel magnetoresistance effect with antiferromagnets, J. Condens. Matter Phys.37, 183003 (2025). 6

  15. [16]

    Bhowal and N

    S. Bhowal and N. A. Spaldin, Ferroically ordered mag- netic octupoles ind-wave altermagnets, Phys. Rev. X 14, 011019 (2024)

  16. [17]

    Krempask´ y, L

    J. Krempask´ y, L. ˇSmejkal, S. W. D’Souza, M. Ha- jlaoui, G. Springholz, K. Uhl´ ıˇ rov´ a, F. Alarab, P. C. Constantinou, V. Strocov, D. Usanov, W. R. Pudelko, R. Gonz´ alez-Hern´ andez, A. Birk Hellenes, Z. Jansa, H. Reichlov´ a, Z. ˇSob´ aˇ n, R. D. Gonzalez Betancourt, P. Wadley, J. Sinova, D. Kriegner, J. Min´ ar, J. H. Dil, and T. Jungwirth, Alterm...

  17. [18]

    Takagi, R

    R. Takagi, R. Hirakida, Y. Settai, R. Oiwa, H. Tak- agi, A. Kitaori, K. Yamauchi, H. Inoue, J.-i. Yamaura, D. Nishio-Hamane, S. Itoh, S. Aji, H. Saito, T. Naka- jima, T. Nomoto, R. Arita, and S. Seki, Spontaneous hall effect induced by collinear antiferromagnetic order at room temperature, Nat. Mater.24, 63 (2025)

  18. [19]

    Reichlova, R

    H. Reichlova, R. Lopes Seeger, R. Gonz´ alez-Hern´ andez, I. Kounta, R. Schlitz, D. Kriegner, P. Ritzinger, M. Lammel, M. Leivisk¨ a, A. Birk Hellenes, K. Olejn´ ık, V. Petˇ riˇ cek, P. Doleˇ zal, L. Horak, E. Schmoranze- rova, A. Badura, S. Bertaina, A. Thomas, V. Baltz, L. Michez, J. Sinova, S. T. B. Goennenwein, T. Jung- wirth, and L. ˇSmejkal, Observa...

  19. [20]

    S. Lee, S. Lee, S. Jung, J. Jung, D. Kim, Y. Lee, B. Seok, J. Kim, B. G. Park, L. ˇSmejkal, C.-J. Kang, and C. Kim, Broken kramers degeneracy in altermag- netic MnTe, Phys. Rev. Lett.132, 036702 (2024)

  20. [21]

    M. Gu, Y. Liu, H. Zhu, K. Yananose, X. Chen, Y. Hu, A. Stroppa, and Q. Liu, Ferroelectric switchable alter- magnetism, Phys. Rev. Lett.134, 106802 (2025)

  21. [22]

    M. Hu, X. Cheng, Z. Huang, and J. Liu, Catalog of c-paired spin-momentum locking in antiferromagnetic systems, Phys. Rev. X15, 021083 (2025)

  22. [23]

    ˇSmejkal, A

    L. ˇSmejkal, A. Marmodoro, K.-H. Ahn, R. Gonz´ alez- Hern´ andez, I. Turek, S. Mankovsky, H. Ebert, S. W. D’Souza, O. ˇSipr, J. Sinova, and T. Jungwirth, Chiral magnons in altermagnetic RuO 2, Phys. Rev. Lett.131, 256703 (2023)

  23. [24]

    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. Natl. Acad. Sci. USA118, e2108924118 (2021)

  24. [25]

    C. L. Tschirhart, M. Serlin, H. Polshyn, A. Shragai, Z. Xia, J. Zhu, Y. Zhang, K. Watanabe, T. Taniguchi, M. E. Huber, and A. F. Young, Imaging orbital ferro- magnetism in a moir´ e chern insulator, Science372, 1323 (2021)

  25. [26]

    Serlin, C

    M. Serlin, C. L. Tschirhart, H. Polshyn, Y. Zhang, J. Zhu, K. Watanabe, T. Taniguchi, L. Balents, and A. F. Young, Intrinsic quantized anomalous hall effect in a moir´ e heterostructure, Science367, 900 (2020)

  26. [27]

    Lin, Y.-H

    J.-X. Lin, Y.-H. Zhang, E. Morissette, Z. Wang, S. Liu, D. Rhodes, K. Watanabe, T. Taniguchi, J. Hone, and J. I. A. Li, Spin-orbit–driven ferromagnetism at half moir´ e filling in magic-angle twisted bilayer graphene, Science375, 437 (2022)

  27. [28]

    Polshyn, J

    H. Polshyn, J. Zhu, M. A. Kumar, Y. Zhang, F. Yang, C. L. Tschirhart, M. Serlin, K. Watanabe, T. Taniguchi, A. H. MacDonald, and A. F. Young, Electrical switching of magnetic order in an orbital chern insulator, Nature 588, 66 (2020)

  28. [29]

    A. L. Sharpe, E. J. Fox, A. W. Barnard, J. Finney, K. Watanabe, T. Taniguchi, M. A. Kastner, and D. Goldhaber-Gordon, Evidence of orbital ferromag- netism in twisted bilayer graphene aligned to hexagonal boron nitride, Nano Lett.21, 4299 (2021)

  29. [30]

    G. Chen, A. L. Sharpe, E. J. Fox, S. Wang, B. Lyu, L. Jiang, H. Li, K. Watanabe, T. Taniguchi, M. F. Crommie, M. A. Kastner, Z. Shi, D. Goldhaber-Gordon, Y. Zhang, and F. Wang, Tunable orbital ferromagnetism at noninteger filling of a moir´ e superlattice, Nano Lett. 22, 238 (2022)

  30. [31]

    J. Xie, Z. Zhang, X. Chen, Y. H. Kwan, Z. Huo, J. Herzog-Arbeitman, L. Guo, K. Watanabe, T. Taniguchi, K. Liu, X. C. Xie, B. A. Bernevig, Z.-D. Song, and X. Lu, Unconventional orbital mag- netism in graphene-based fractional chern insulators (2025), arXiv:2506.01485 [cond-mat.mes-hall]

  31. [32]

    T. Han, Z. Lu, G. Scuri, J. Sung, J. Wang, T. Han, K. Watanabe, T. Taniguchi, L. Fu, H. Park, and L. Ju, Orbital multiferroicity in pentalayer rhombohe- dral graphene, Nature623, 41 (2023)

  32. [33]

    T. Han, Z. Lu, Y. Yao, J. Yang, J. Seo, C. Yoon, K. Watanabe, T. Taniguchi, L. Fu, F. Zhang, and L. Ju, Large quantum anomalous hall effect in spin-orbit proximitized rhombohedral graphene, Science384, 647 (2024)

  33. [34]

    J. Xie, Z. Huo, X. Lu, Z. Feng, Z. Zhang, W. Wang, Q. Yang, K. Watanabe, T. Taniguchi, K. Liu, Z. Song, X. C. Xie, J. Liu, and X. Lu, Tunable fractional chern insulators in rhombohedral graphene superlattices, Nat. Mater.24, 1042 (2025)

  34. [35]

    Huang, T

    C. Huang, T. M. R. Wolf, W. Qin, N. Wei, I. V. Blinov, and A. H. MacDonald, Spin and orbital metallic mag- netism in rhombohedral trilayer graphene, Phys. Rev. B107, L121405 (2023)

  35. [36]

    Das and C

    M. Das and C. Huang, Unconventional metallic ferro- magnetism: Nonanalyticity and sign-changing behav- ior of orbital magnetization in rhombohedral trilayer graphene, Phys. Rev. B109, L060409 (2024)

  36. [37]

    Mu and J

    X. Mu and J. Zhou, Valley-dependent giant orbital mo- ments and transport features in rhombohedral graphene multilayers, Phys. Rev. B111, 165102 (2025)

  37. [38]

    L. M. Sandratskii and J. K¨ ubler, Role of orbital polar- ization in weak ferromagnetism, Phys. Rev. Lett.76, 4963 (1996)

  38. [39]

    Shindou and N

    R. Shindou and N. Nagaosa, Orbital ferromagnetism and anomalous hall effect in antiferromagnets on the distorted fcc lattice, Phys. Rev. Lett.87, 116801 (2001)

  39. [40]

    Ito and K

    N. Ito and K. Nomura, Anomalous hall effect and spon- taneous orbital magnetization in antiferromagnetic weyl metal, J. Phys. Soc. Jpn.86, 063703 (2017)

  40. [41]

    D. Jo, D. Go, Y. Mokrousov, P. M. Oppeneer, S.-W. Cheong, and H.-W. Lee, Weak ferromagnetism in al- termagnets from alternatingg-tensor anisotropy, Phys. Rev. Lett.134, 196703 (2025)

  41. [42]

    Nersesyan and G

    A. Nersesyan and G. Vachnadze, Low-temperature ther- modynamics of the two-dimensional orbital antiferro- magnet, J. Low Temp. Phys.77, 293 (1989)

  42. [43]

    Varma, Mind the pseudogap, Nature468, 184 (2010)

    C. Varma, Mind the pseudogap, Nature468, 184 (2010)

  43. [44]

    C. M. Varma, Non-fermi-liquid states and pairing insta- bility of a general model of copper oxide metals, Phys. Rev. B55, 14554 (1997)

  44. [45]

    C. M. Varma, Pseudogap phase and the quantum- critical point in copper-oxide metals, Phys. Rev. Lett. 7 83, 3538 (1999)

  45. [46]

    C. M. Varma, Theory of the pseudogap state of the cuprates, Phys. Rev. B73, 155113 (2006)

  46. [47]

    Shekhter and C

    A. Shekhter and C. M. Varma, Considerations on the symmetry of loop order in cuprates, Phys. Rev. B80, 214501 (2009)

  47. [48]

    C. M. Varma, Pseudogap in cuprates in the loop-current ordered state, J. Phys. Condens. Matter26, 505701 (2014)

  48. [49]

    Bulut, A

    S. Bulut, A. P. Kampf, and W. A. Atkinson, Instabil- ity towards staggered loop currents in the three-orbital model for cuprate superconductors, Phys. Rev. B92, 195140 (2015)

  49. [50]

    R. B. Laughlin, Fermi-liquid computation of the phase diagram of high-T c cuprate superconductors with an orbital antiferromagnetic pseudogap, Phys. Rev. Lett. 112, 017004 (2014)

  50. [51]

    V. Leeb, A. Mook, L. ˇSmejkal, and J. Knolle, Sponta- neous formation of altermagnetism from orbital order- ing, Phys. Rev. Lett.132, 236701 (2024)

  51. [52]

    Siddharthan and A

    R. Siddharthan and A. Georges, Square kagome quan- tum antiferromagnet and the eight-vertex model, Phys. Rev. B65, 014417 (2001)

  52. [53]

    Richter, O

    J. Richter, O. Derzhko, and J. Schulenburg, Magnetic- field induced spin-peierls instability in strongly frus- trated quantum spin lattices, Phys. Rev. Lett.93, 107206 (2004)

  53. [54]

    A. W. Glaetzle, M. Dalmonte, R. Nath, I. Rousochatza- kis, R. Moessner, and P. Zoller, Quantum spin-ice and dimer models with rydberg atoms, Phys. Rev. X4, 041037 (2014)

  54. [55]

    Thonhauser, D

    T. Thonhauser, D. Ceresoli, D. Vanderbilt, and R. Resta, Orbital magnetization in periodic insulators, Phys. Rev. Lett.95, 137205 (2005)

  55. [56]

    Ceresoli, T

    D. Ceresoli, T. Thonhauser, D. Vanderbilt, and R. Resta, Orbital magnetization in crystalline solids: Multi-band insulators, chern insulators, and metals, Phys. Rev. B74, 024408 (2006)

  56. [57]

    Resta, D

    R. Resta, D. Ceresoli, T. Thonhauser, and D. Vander- bilt, Orbital magnetization in extended systems, Chem. Phys. Chem.6, 1815 (2005)

  57. [58]

    J. Shi, G. Vignale, D. Xiao, and Q. Niu, Quantum the- ory of orbital magnetization and its generalization to interacting systems, Phys. Rev. Lett.99, 197202 (2007)

  58. [59]

    Resta, Electrical polarization and orbital magneti- zation: the modern theories, J

    R. Resta, Electrical polarization and orbital magneti- zation: the modern theories, J. Phys.: Condens.Matter 22, 123201 (2010)

  59. [60]

    Thonhauser, Theory of orbital magnetization in solids, Int

    T. Thonhauser, Theory of orbital magnetization in solids, Int. J. Mod. Phys. B25, 1429 (2011)

  60. [61]

    Xiao, M.-C

    D. Xiao, M.-C. Chang, and Q. Niu, Berry phase ef- fects on electronic properties, Rev. Mod. Phys.82, 1959 (2010)

  61. [62]

    Bianco and R

    R. Bianco and R. Resta, Orbital magnetization as a lo- cal property, Phys. Rev. Lett.110, 087202 (2013)

  62. [63]

    Marrazzo and R

    A. Marrazzo and R. Resta, Locality of the anomalous hall conductivity, Phys. Rev. B95, 121114 (2017)

  63. [64]

    S.-S. Wang, Y. Yu, J.-H. Guan, Y.-M. Dai, H.-H. Wang, and Y.-Y. Zhang, Boundary effects on orbital magneti- zation for a bilayer system with different chern numbers, Phys. Rev. B106, 075136 (2022)

  64. [65]

    Bhowal and G

    S. Bhowal and G. Vignale, Orbital Hall effect as an al- ternative to valley hall effect in gapped graphene, Phys. Rev. B103, 195309 (2021)

  65. [66]

    Zeng and Y.-J

    S. Zeng and Y.-J. Zhao, Description of two-dimensional altermagnetism: Categorization using spin group the- ory, Phys. Rev. B110, 054406 (2024)

  66. [67]

    Cheong and F.-T

    S.-W. Cheong and F.-T. Huang, Altermagnetism classi- fication, npj Quantum Mater.10, 38 (2025)

  67. [68]

    P. A. McClarty and J. G. Rau, Landau theory of alter- magnetism, Phys. Rev. Lett.132, 176702 (2024)

  68. [69]

    [87–89, 92, 106–118]

    See Supplemental Material at http://link.aps.org/supplemental/xxx, for more details about the expressions of orbital magnetization in reciprocal and real spaces, magnetic multipoles, the formula for nonlinear current-induced magnetization, detailed symmetry analysis of orbital altermagnetism, the first-principles calculation method, and more numerical res...

  69. [70]

    M. E. Simon and C. M. Varma, Detection and impli- cations of a time-reversal breaking state in underdoped cuprates, Phys. Rev. Lett.89, 247003 (2002)

  70. [71]

    Chakravarty, R

    S. Chakravarty, R. B. Laughlin, D. K. Morr, and C. Nayak, Hidden order in the cuprates, Phys. Rev. B 63, 094503 (2001)

  71. [72]

    H. A. Mook, P. Dai, and F. Do˘ gan, Observation of magnetic moments in the superconducting state of YBa2Cu3O6.6, Phys. Rev. B64, 012502 (2001)

  72. [73]

    Chakravarty, H.-Y

    S. Chakravarty, H.-Y. Kee, and C. Nayak, Neutron scat- tering signature of d-density wave order in the cuprates, Int. J. Mod. Phys. B15, 2901 (2001)

  73. [74]

    Kee and Y

    H.-Y. Kee and Y. B. Kim, Specific-heat anomaly in the d density wave state and emergence of inhomogeneous or- bital antiferromagnetic order, Phys. Rev. B66, 012505 (2002)

  74. [75]

    V. I. Belyavsky, Y. V. Kopaev, and M. Y. Smirnov, Interplay of the superconducting state and orbital an- tiferromagnetic state of the high-temperature cuprate superconductors, Phys. Rev. B72, 132501 (2005)

  75. [76]

    D. F. Schroeter and S. Doniach, Orbital antiferromag- netism in coupled planar systems, Phys. Rev. B69, 094407 (2004)

  76. [77]

    F. J. Ohkawa, Orbital antiferromagnetism in ceb6, J. Phys. Soc. Jpn.54, 3909 (1985)

  77. [78]

    hidden order

    H.-H. Kung, S. Ran, N. Kanchanavatee, V. Krapivin, A. Lee, J. A. Mydosh, K. Haule, M. B. Maple, and G. Blumberg, Analogy between the “hidden order” and the orbital antiferromagnetism in URu2−xFexSi2, Phys. Rev. Lett.117, 227601 (2016)

  78. [79]

    M. Vila, V. Sunko, and J. E. Moore, Orbital-spin locking and its optical signatures in altermagnets, Phys. Rev. B 112, L020401 (2025)

  79. [80]

    Zhao, T.-L

    L. Zhao, T.-L. Hung, C.-C. Li, Y.-Y. Chen, M.-K. Wu, R. K. Kremer, M. G. Banks, A. Simon, M.-H. Whangbo, C. Lee, J. S. Kim, I. Kim, and K. H. Kim, CuBr 2 – a new multiferroic material with high critical tempera- ture, Adv. Mater.24, 2469 (2012)

  80. [81]

    Q. Ji, C. Li, J. Wang, J. Niu, Y. Gong, Z. Zhang, Q. Fang, Y. Zhang, J. Shi, L. Liao, X. Wu, L. Gu, Z. Liu, and Y. Zhang, Metallic vanadium disulfide nanosheets as a platform material for multifunctional electrode ap- plications, Nano Lett.17, 4908 (2017)

Showing first 80 references.