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REVIEW 3 major objections 5 minor 5 cited by

Quantum transport theory for unconventional magnets: Interplay of altermagnetism and p-wave magnetism with superconductivity

T0 review · 3 major / 5 minor · reviewed 2026-08-11 · deepseek-v4-flash

Pith's one-line read The paper derives a single symmetry-constrained nonlinear-sigma-model action whose saddle point yields diffusive transport equations for ferromagnets, antiferromagnets, altermagnets, and p-wave magnets, in both normal and superconducting…

desk verdict A symmetry-based NLSM framework for exchange magnets that mostly delivers; the new transport effects are real consequences of the allowed terms, but their magnitude depends on coefficients the paper does not compute. read the letter →

arxiv 2412.10236 v4 pith:RBGVF5VW submitted 2024-12-13 cond-mat.supr-con

classification cond-mat.supr-con
keywords nonlinearsigmamodelUsadelequationaltermagnetismp-wavemagnetismdiffusivetransportsuperconductingproximityeffectspin-polarizedcurrentsspin-galvanic
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

This paper aims to establish a single low-energy transport theory for diffusive magnetic metals in which magnetism comes from exchange interactions, valid in both the normal and superconducting states. The authors construct the most general nonlinear-sigma-model action allowed by charge-conjugation, chronology, and spin-space-group symmetries up to second order in spatial gradients and first order in the exchange coupling. The saddle-point equations of this action reduce to the usual quasiclassical Usadel equations in standard limits but contain extra symmetry-allowed gradient terms. Those terms predict spin-dependent diffusion and spin-polarized currents in ferromagnets, the diffusive spin-splitter effect in altermagnets, a spontaneous magnetization at superconductor/altermagnet interfaces, and a temperature-dependent spin-galvanic effect in p-wave magnets. If correct, the theory provides a general framework for nonequilibrium transport in arbitrary magnetic systems combined with superconductivity.

What carries the argument

The central object is the effective action $S_M[Q]$ in Eq. (22), a Keldysh nonlinear $\sigma$ model for the soft-mode matrix field $Q$, which at the saddle point equals the quasiclassical Green's function $g$. The action contains the standard diffusion, time-derivative, pairing, exchange-field, and spin-relaxation terms, and adds the symmetry-allowed third-rank tensor terms $\gamma_{ajk}\tau_3\sigma_a\partial_j Q\partial_k Q$ and $i\chi_{ajk}\tau_3\sigma_a Q\partial_j Q\partial_k Q$. The spin space group, the set of independent real-space and spin-space symmetry operations under which the crystal is invariant, determines which tensor components survive. Charge conjugation forces the tensors to be symmetric in the spatial indices, and chronology symmetry forces the coefficients to be real. Varying the action under the constraint $Q^2=1$ produces the matrix current and torque in Eqs. (24)-(25), whose continuity equation is the generalized Usadel equation; for p-wave magnets an additional second-order-in-exchange term with tensor $\beta_{kc}$ is added in Eq. (84).

What would settle it

Measure the temperature dependence of the spin-galvanic coefficient in a superconducting p-wave magnet in a Zeeman field and compare it with Eq. (92): the paper predicts a smooth drop of the coefficient to $1/3$ of its normal-state value as $T\to 0$, whereas a spin-orbit-only contribution would be temperature independent. A flat curve would falsify the exchange-driven mechanism.

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Extended reading notes

Core claim

The paper's central claim is that a single Keldysh nonlinear sigma model action, Eq. (22), containing only terms allowed by charge conjugation, chronology symmetry, and the material's spin space group, is a complete low-energy description of diffusive transport in exchange-dominated magnets, in normal and superconducting states. At the saddle point this action yields the generalized Usadel equations, Eqs. (23)-(25). The new symmetry-allowed gradient terms add phenomena absent from the standard quasiclassical equations: a spin-dependent diffusion renormalization and spin-polarized currents in ferromagnets; the diffusive spin-splitter effect in altermagnets, with no superconducting analogue; the proximity-induced magnetization at superconductor-altermagnet interfaces; and a temperature-dependent spin-galvanic effect in p-wave magnets that can be distinguished from the spin-orbit-induced effect only in the superconducting state. The authors also find that only d-wave altermagnets acquire the new transport tensors in the diffusive limit, while g-wave and i-wave altermagnets behave like conventional antiferromagnets in their dirty-limit transport properties.

Load-bearing premise

The derivation assumes that the symmetry-allowed coefficients $\gamma$, $\chi$, $K$, and $\beta$ are generically nonzero in real materials, and that no neglected higher-order or spin-orbit term cancels or overwhelms the effects they produce.

Editorial extensions

If this is right

  • In ferromagnets, an applied charge current automatically carries a spin-polarized current, with spin-dependent conductivities $\sigma_{\uparrow,\downarrow}=\frac{1}{2}\sigma_D(1\pm\gamma P)$; in Josephson junctions with three noncoplanar ferromagnetic domains this produces an anomalous current proportional to $\gamma\,\mathbf{m}_3\cdot(\mathbf{m}_1\times\mathbf{m}_2)$.
  • In the normal state of diffusive d-wave altermagnets, a charge current creates a transverse spin accumulation, the spin-splitter effect, whose sign and magnitude are set by the tensor $T_{jk}$; the effect vanishes for supercurrents, where the magnetization is even under current reversal.
  • In superconductor/altermagnet bilayers, gradients in the superconducting pair amplitude generate an equilibrium magnetization localized near the interface, with the sign pattern determined by the d-wave lobe orientation and no external current required.
  • In p-wave magnets, the spin-galvanic effect is indistinguishable from the spin-orbit-induced one in the normal state, but in the superconducting state its coefficient depends on temperature and falls to one third of its normal-state value at $T=0$.
  • Because the action is not linearized in the superconducting order parameter, the resulting transport theory describes equilibrium and nonequilibrium situations at arbitrary temperatures, both well below and above the critical temperature.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Beyond the paper: the same diffusive framework implies that altermagnetic spin splitting survives in disordered films, not only in ideal clean crystals, so a dirty polycrystalline altermagnet should still accumulate opposite spins on opposite edges under a charge current.
  • Beyond the paper: the predicted pattern of proximity-induced magnetization around a superconducting island, same sign on opposite sides and opposite sign on perpendicular sides, could be used as a non-invasive magnetic probe of altermagnetic lobe orientation in scanning magnetometry.
  • Beyond the paper: if the temperature signature of the p-wave spin-galvanic effect holds, the same experiment could separate exchange-driven from spin-orbit-driven band splitting in materials where both mechanisms are present, a distinction the paper identifies but does not fully exploit.
  • Beyond the paper: because the action is built from symmetry at fixed order in gradients, its predictive power will be strongest when the coefficients $\gamma$, $\chi$, $K$, and $\beta$ are measured across materials with different disorder levels; systematic variations would show where the gradient expansion breaks down.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 5 minor

Summary. This paper develops a Keldysh nonlinear-sigma-model (NLSM) theory for diffusive metals with exchange-type magnetism, covering ferromagnets, antiferromagnets, altermagnets, and p-wave magnets in both normal and superconducting states. The effective action (Eq. (22)) is constructed by enumerating all terms allowed by charge conjugation (Eqs. (12), (15)), chronology symmetry (Eq. (16)), and spin-space-group symmetries up to second order in spatial gradients and first or second order in the exchange coupling τ3σ; the Usadel-type transport equations follow as saddle-point equations (Eqs. (23)-(25)). The authors then derive consequences for each material class: spin-dependent diffusion renormalization and spin-polarized normal and supercurrents in ferromagnets (Sec. IV); a diffusive spin-splitter effect, its absence for supercurrents, and a proximity-induced equilibrium magnetization in d-wave altermagnets (Sec. V); and a temperature-dependent spin-galvanic effect in p-wave magnets with the parameter-free ratio β(T) of Eq. (92) and Fig. 3. Detailed boundary-value solutions are provided in Appendices C through G.

Significance. If the framework is accepted, it provides a unified symmetry-based transport theory for unconventional magnets, going beyond the standard quasiclassical equations and yielding falsifiable predictions. Its strengths are the transparency of the symmetry construction (Appendix A is a systematic enumeration of allowed terms; Appendix F gives explicit symmetry proofs for the absence of the superconducting spin-splitter), the parameter-free spin-galvanic ratio β(T) in Eq. (92) with a correct and easily verified low-temperature limit of 1/3, concrete device predictions (spin accumulations at sample edges, the lobe-dependent magnetization pattern of Fig. 2), and the useful tensor classification in Table I. The stress-test concern that all new effects are proportional to symmetry-allowed but microscopically uncomputed coefficients does partially land: the paper proves only that γ, χ, T, K, and β are permitted, not that they are generically nonzero, so the central predictions are conditional. Within the effective-theory logic this is the standard status of undetermined couplings, but given the prominence of the new effects, the contingency deserves explicit treatment.

major comments (3)
  1. [Sec. III (after Eq. (21)); Table I; Eqs. (64)-(66), (80)-(81), (84)-(92)] All of the new physical effects reported in Secs. IV-VI are proportional to the symmetry-allowed coefficients γ, χ, T, K, and β introduced in Eqs. (22) and (84). The manuscript establishes only that these coefficients are permitted by charge conjugation, chronology, and the relevant spin space group; it never computes or bounds them from a microscopic model. This is load-bearing, not cosmetic: in Table I the groups 24/1m and 22/2m have two independent tensor components, so T and K are unrelated by symmetry, and a microscopic model could give T ≠ 0 with K = 0. That would eliminate the proximity-induced magnetization in Eqs. (80)-(81) while leaving the normal-state spin-splitter in Eqs. (64)-(66) intact. Likewise, β_xz in Eq. (84) could vanish at leading order in disorder or be canceled by spin-orbit terms of the same tensor structure, in which case the temperature dependence in Fig. 3 would not discriminate the exchange mechanism. The text after Eq. (21) states that the coefficients are assumed small relative to the diffusion contribution, but not that they are generically nonzero. I request either a microscopic estimate for at least one material class (for example, a two-dimensional tight-binding altermagnet or ferromagnet with short-range disorder, computing γ, χ, T, and K in the Born approximation) or an explicit discussion of the mechanisms that generate these coefficients and the conditions under which each predicted effect survives.
  2. [Sec. V.B, Eqs. (80)-(81); Appendix G, Eq. (G10)] There is a quantitative inconsistency in the headline proximity-magnetization result. Evaluating Eq. (80) at x = 0 using Σ_n (2n+1)^{-3} = 7ζ(3)/8 gives Mz(0) = -(7ζ(3)/16) gμB Pz Kxx πν γ_B^2 |Δ|^2 D/(πT)^2, whereas Eq. (81) reports the prefactor 7ζ(3)/4 with the same remaining factors: a discrepancy of exactly a factor of 4. In addition, the corresponding appendix formula, Eq. (G10), prints (πT)^3 in the denominator, which is dimensionally inconsistent with the (πT)^2 appearing in Eq. (80) and Eq. (G9). The factor-of-4 discrepancy must be reconciled, and the denominator in Eq. (G10) corrected, before the quoted interface value can be used.
  3. [Sec. V.B; Appendix F 3] The paper claims that the superconducting spin-splitter effect predicted in Ref. [30] (example 1a) is absent, supported by the symmetry arguments in Appendix F (Mz(q) = Mz(-q); Mz = 0 in the transverse orientation, Eqs. (70)-(72)). These arguments appear internally consistent. However, the manuscript does not identify where the calculation of Ref. [30] fails: whether the source is the linearization in the pair amplitudes, the specific electron-gas model used there, or a difference in the assumed spin space group. Because the absence of the superfluid spin-splitter is a central claim of Sec. V.B and is explicitly contrasted with Ref. [30], the authors should analyze the origin of the discrepancy rather than merely stating the contrast.
minor comments (5)
  1. [Abstract; Sec. I (outline paragraph)] The abstract contains two garbled passages: 'we show that spin-galvanic effects which are distinguishable from the spin-galvanic effect induced by spin-orbit coupling only in the superconducting state' is missing a verb, and 'inversionsymmetry broken antiferromagnets' is missing a hyphen. In the paper outline in Sec. I, 'In Sec. VI we extend our model to second order to higher order to capture spin-galvanic effects' is garbled and should be rewritten.
  2. [Fig. 3 caption] The caption 'normalized its the normal state value' should read 'normalized to its normal-state value'; it would also help to state explicitly that the SOC-induced coefficient is temperature-independent and equal to 1 on this normalization.
  3. [Appendix F 2] The symbol χaxy appears where the tensor Kxy is meant, and the transformation equations in this appendix mix χ and γ symbols with the K tensor; the notation should be made uniform with Eqs. (59)-(61) and Table I.
  4. [Sec. III, paragraph after Eq. (18)] The first-order derivative term Tr{αaj σa τ3 ∂jQ} is discarded as a total derivative that renormalizes the exchange field at boundaries. Since several central results, notably the proximity-induced magnetization in Appendix G and the spin-polarized currents in Appendix C, are boundary-sensitive, the authors should state whether αaj is forbidden by the spin space groups of each material class and, where allowed, justify the neglect of its boundary renormalization.
  5. [Sec. V.B, Eqs. (74)-(79) and Appendix G 1] The relation between f± and the singlet/triplet amplitudes (fs, ft) is introduced as f± = fs ± ift sign(ωn) in Sec. V.B but is used with slightly different sign and imaginary-unit conventions in Appendix G; stating one explicit convention would allow the reader to verify Eqs. (80)-(81) directly.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: symmetry-enumerated action is the input; effects are derived consequences with coefficients left as free parameters.

full rationale

The paper's central derivation is the construction of the NLSM action in Eq. (22) by enumerating all scalars allowed by charge conjugation, chronology, and spin-space-group symmetries up to second order in gradients and first order in tau3 sigma. Appendix A carries out this enumeration explicitly, including proofs that the kappa term vanishes and that gamma and chi are real with symmetric spatial indices. The subsequent Usadel equations (23-25) are the saddle-point equations of this action. The physical effects (spin-dependent diffusion, normal-state spin-splitter, proximity magnetization, p-wave spin-galvanic effect) are algebraic consequences of the corresponding symmetry-allowed coefficients gamma, T, K, and beta. These coefficients are not fitted to any measured quantity and are not defined in terms of the predicted observables; they play the same role as D and Gamma in the standard NLSM. The p-wave ratio beta(T) in Eq. (92) is parameter-free because beta_xz cancels, and the proximity magnetization in Eqs. (80)-(81) is an explicit solution of the linearized Usadel equation with prescribed boundary conditions, not a restatement of the K term. The self-citations [31-33] supply the chronology-symmetry method and earlier SOC Usadel constructions, but the paper states the symmetry conditions itself (Eqs. 15-16) and rederives the terms in Appendix A, so no load-bearing claim rests solely on a self-citation. The acknowledged limitation that the coefficients' magnitudes are not fixed by symmetry is a substantive correctness and assumption gap (for example, K could vanish accidentally or be overwhelmed by neglected higher-order terms), but it is not circularity: the derivation would be valid for any value of the coefficients, and the paper does not use the predicted effects as evidence for the coefficients. Therefore, the derivation chain is self-contained in the sense relevant to the circularity pass.

Assumptions & free parameters 4 free parameters · 5 assumptions · 0 invented entities

The paper's predictive power comes from symmetry classification; the numerical coefficients gamma, chi, K, and beta remain free parameters, so many predictions are qualitative or directional rather than quantitative. However, the p-wave spin-galvanic ratio beta(T)/beta_N in Eq. (92) is parameter-free, and the geometry of the proximity-induced magnetization is robust, which keeps the circularity burden low. No new particles or fields are introduced.

free parameters (4)
  • gamma = unknown, free coefficient
    Introduced in Eq. (30) as the coefficient of P_a sigma_a tau3 (grad Q)^2; it controls the spin-dependent diffusion renormalization and spin-polarized currents in ferromagnets. Its magnitude is not fixed by symmetry.
  • chi = unknown, free coefficient
    Introduced in Eq. (30) as the coefficient of P_a sigma_a tau3 Q (grad Q)^2; it controls the gradient Hanle correction. Its magnitude is not fixed by symmetry.
  • K_jk and T_jk tensor components = unknown, free coefficients
    Altermagnet tensors in Eq. (58), whose nonzero components are fixed by spin space groups (Table I) but whose overall magnitude is left as a free parameter. They generate the normal-state spin-splitter and the superconducting proximity magnetization.
  • beta_xz = unknown, free coefficient
    Spin-galvanic coefficient in the p-wave magnet action, Eq. (84). Its temperature dependence is predicted, but its absolute value is not derived from a microscopic model.
assumptions (5)
  • domain assumption The Keldysh nonlinear sigma model with the soft-mode constraint Q^2 = 1 describes diffusive conductors in both normal and superconducting states.
    Invoked throughout Sec. II to set up the generating functional and identify the saddle point with the quasiclassical Green's function.
  • standard math Charge conjugation symmetry, Eq. (15), and chronology symmetry, Eq. (16), are exact constraints on the action.
    These follow from the Nambu structure and causality; used in Sec. III and Appendix A to select all allowed terms in the action.
  • ad hoc to paper The effective action can be truncated at second order in spatial derivatives and first order in the exchange-coupling factor tau3 sigma, with the new coefficients assumed small.
    Stated in Sec. III: the expansion 'in tau3 sigma_a assumes these coefficients are small compared to the usual diffusion contribution.' This truncation is a modeling choice that determines which effects are retained.
  • domain assumption Spin-orbit coupling terms are negligible compared with exchange interactions in the materials considered.
    Argued in Sec. I: exchange interactions are nonrelativistic and dominate, so spin space groups apply and SOC-induced transport terms are ignored.
  • domain assumption The spin space group classification correctly determines the allowed components of the tensors T_jk and K_jk.
    Used in Sec. V and Appendix D to produce Table I; assumes the materials realize the listed spin space groups and that the mesoscopic coarse-graining preserves these symmetries.

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Pith. "Pith review of Quantum transport theory for unconventional magnets: Interplay of altermagnetism and p-wave magnetism with superconductivity." pith.science (2026). https://pith.science/paper/RBGVF5VW

@misc{pith2026241210236,
  author       = {Pith},
  title        = {Pith review of: Quantum transport theory for unconventional magnets: Interplay of altermagnetism and p-wave magnetism with superconductivity},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/RBGVF5VW}},
  note         = {Machine review of arXiv:2412.10236}
}
read the original abstract

We present a quantum transport theory for generic magnetic metals, in which magnetism occurs predominantly due to exchange interactions, such as ferromagnets, antiferromagnets, altermagnets and p-wave magnets. Our theory is valid both for the normal and the superconducting state. We derive the effective low-energy action for each of these materials, where the spin space groups are used to determine the form of the tensor coefficients appearing in the action. The transport equations, which are obtained as the saddle point equations of this action, describe a wider range of phenomena than the usual quasiclassical equations. In ferromagnets, in addition to the usual exchange field and spin relaxation effects, we identify a spin-dependent renormalization of the diffusion coefficient, which provides a description of spinpolarized currents in both the normal and superconducting equal spin-triplet states. In the normal state, our equations provide a complete description of the spin-splitting effect in diffusive systems, recently predicted in ideal clean altermagnets. In the superconducting state, our equations predict a proximity induced magnetization, the appearance of a spontaneous magnetic moment in hybrid superconductor-altermagnet systems. The distribution and polarization direction of this magnetic moment depend on the symmetry of the structure, thus measurements of such polarization reveal the underlying microscopic symmetry of the altermagnet. Finally, for inversionsymmetry broken antiferromagnets, such as the p-wave magnet, we show that spin-galvanic effects which are distinguishable from the spin-galvanic effect induced by spin-orbit coupling only in the superconducting state. Besides these examples, our model applies to arbitrary magnetic systems, providing a complete theory for nonequilibrium transport in diffusive nonconventional magnets at arbitrary temperatures.

Figures

Figures reproduced from arXiv: 2412.10236 by the authors.

Figure 1
Figure 1. FIG. 1. A Josephson junction in which the weak link consists [PITH_FULL_IMAGE:figures/full_fig_p010_1.png] view at source ↗
Figure 2
Figure 2. FIG. 2. Three types of S / AM junctions in which a local magnetization is generated, indicated using green (spin up) and [PITH_FULL_IMAGE:figures/full_fig_p014_2.png] view at source ↗
Figure 3
Figure 3. FIG. 3. The magnitude of the spin-galvanic coefficient in the [PITH_FULL_IMAGE:figures/full_fig_p016_3.png] view at source ↗
Figures from the paper (2 more)
Figure 4
Figure 4. Figure 4: FIG. 4. The S / [PITH_FULL_IMAGE:figures/full_fig_p026_4.png]
Figure 5
Figure 5. Figure 5: FIG. 5. The transverse spin accumulation in a finite size 2D altermagnet with [PITH_FULL_IMAGE:figures/full_fig_p041_5.png]

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Forward citations

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Reference graph

Works this paper leans on

115 extracted references · 59 canonical work pages · cited by 5 Pith papers

  1. [98]

    Zarzuela, R

    R. Zarzuela, R. Jaeschke-Ubiergo, O. Gomonay, L. ˇSmejkal, and J. Sinova, arXiv preprint arXiv:2412.13763 10.48550/arXiv.2412.13763 (2024)

  2. [30]

    H. G. Giil, B. Brekke, J. Linder, and A. Brataas, arXiv preprint arXiv:2403.04851 10.48550/arXiv.2403.04851 (2024)

  3. [92]

    A. A. Zyuzin, Phys. Rev. B 109, L220505 (2024)

  4. [1]

    A. I. Buzdin, Rev. Mod. Phys. 77, 935 (2005)

  5. [2]

    F. S. Bergeret, A. F. Volkov, and K. B. Efetov, Rev. Mod. Phys. 77, 1321 (2005)

  6. [3]

    Eschrig, Physics Today 64, 43 (2011)

    M. Eschrig, Physics Today 64, 43 (2011)

  7. [4]

    Linder and J

    J. Linder and J. W. Robinson, Nature Physics 11, 307 (2015)

  8. [5]

    ˇSmejkal, J

    L. ˇSmejkal, J. Sinova, and T. Jungwirth, Phys. Rev. X 12, 031042 (2022)

Show all 115 references
  1. [6]

    A. B. Hellenes, T. Jungwirth, J. Sinova, and L. ˇSmejkal, arXiv preprint arXiv:2309.01607 10.48550/arXiv.2309.01607 (2023)

  2. [7]

    ˇSmejkal, J

    L. ˇSmejkal, J. Sinova, and T. Jungwirth, Phys. Rev. X 12, 040501 (2022)

  3. [8]

    Jungwirth, R

    T. Jungwirth, R. M. Fernandes, J. Sinova, and L. Smejkal, arXiv preprint arXiv:2409.10034 10.48550/arXiv.2409.10034 (2024)

  4. [9]

    Reimers, L

    S. Reimers, L. Odenbreit, L. ˇSmejkal, V. N. Strocov, P. Constantinou, A. B. Hellenes, R. Jaeschke Ubiergo, W. H. Campos, V. K. Bharadwaj, A. Chakraborty, et al. , Nature Communications 15, 2116 (2024)

  5. [10]

    Fedchenko, J

    O. Fedchenko, J. Min´ ar, A. Akashdeep, S. W. D’Souza, D. Vasilyev, O. Tkach, L. Odenbreit, Q. Nguyen, D. Kutnyakhov, N. Wind, et al. , Science advances 10, eadj4883 (2024)

  6. [11]

    Y. Guo, J. Zhang, Z. Zhu, Y.-y. Jiang, L. Jiang, C. Wu, J. Dong, X. Xu, W. He, B. He, et al., Advanced Science , 2400967 (2024)

  7. [12]

    S. Das, D. Suri, and A. Soori, Journal of Physics: Con- densed Matter 35, 435302 (2023)

  8. [13]

    L. Bai, W. Feng, S. Liu, L. ˇSmejkal, Y. Mokrousov, and Y. Yao, Advanced Functional Materials , 2409327 (2024)

  9. [14]

    Zhang, X

    X.-P. Zhang, X. Fan, X. Wang, and Y. Yao, arXiv preprint arXiv:2409.10088 10.48550/arXiv.2409.10088 (2024)

  10. [15]

    Gomonay, V

    O. Gomonay, V. Kravchuk, R. Jaeschke-Ubiergo, K. Yershov, T. Jungwirth, L. ˇSmejkal, J. Brink, and J. Sinova, arXiv preprint arXiv:2403.10218 (2024)

  11. [16]

    Maeda, B

    K. Maeda, B. Lu, K. Yada, and Y. Tanaka, Journal of the Physical Society of Japan 93, 114703 (2024)

  12. [17]

    Sukhachov and J

    P. Sukhachov and J. Linder, Phys. Rev. B 110, 205114 (2024)

  13. [18]

    Brekke, P

    B. Brekke, P. Sukhachov, H. G. Giil, A. Brataas, and J. Linder, arXiv preprint arXiv:2405.15823 10.48550/arXiv.2405.15823 (2024)

  14. [19]

    Sivianes, F

    J. Sivianes, F. J. d. Santos, and J. Iba˜ nez-Azpiroz, arXiv preprint arXiv:2406.19842 10.48550/arXiv.2406.19842 (2024)

  15. [20]

    B. Lu, K. Maeda, H. Ito, K. Yada, and Y. Tanaka, Phys. Rev. Lett. 133, 226002 (2024)

  16. [21]

    Fukaya, K

    Y. Fukaya, K. Maeda, K. Yada, J. Cayao, Y. Tanaka, and B. Lu, arXiv preprint arXiv:2411.02679 10.48550/arXiv.2411.02679 (2024)

  17. [22]

    Mondal, A

    D. Mondal, A. Pal, A. Saha, and T. Nag, arXiv preprint arXiv:2409.08009 10.48550/arXiv.2409.08009 (2024)

  18. [23]

    Yang, Z.-X

    J. Yang, Z.-X. Liu, and C. Fang, Nature Communica- tions 15, 10203 (2024)

  19. [24]

    Li and C.-C

    Y.-X. Li and C.-C. Liu, Phys. Rev. B 108, 205410 (2023)

  20. [25]

    Li, Phys

    Y.-X. Li, Phys. Rev. B 109, 224502 (2024)

  21. [26]

    A. I. Larkin and Y. N. Ovchinnikov, in Nonequilibrium superconductivity, edited by D. N. Langenberg and A. I. Larkin (Elsevier, Amsterdam, 1986) p. 493

  22. [27]

    E. H. Fyhn, A. Brataas, A. Qaiumzadeh, and J. Linder, Phys. Rev. B 107, 174503 (2023)

  23. [28]

    G. A. Bobkov, I. V. Bobkova, A. M. Bobkov, and A. Kamra, Phys. Rev. B 106, 144512 (2022)

  24. [29]

    G. A. Bobkov, I. V. Bobkova, and A. M. Bobkov, Phys. Rev. B 108, 054510 (2023)

  25. [31]

    Virtanen, F

    P. Virtanen, F. S. Bergeret, and I. V. Tokatly, Phys. Rev. B 104, 064515 (2021)

  26. [32]

    Virtanen, F

    P. Virtanen, F. S. Bergeret, and I. V. Tokatly, Phys. Rev. B 105, 224517 (2022)

  27. [33]

    Kokkeler, F

    T. Kokkeler, F. S. Bergeret, and I. Tokatly, arXiv preprint arXiv:2405.06334 10.48550/arXiv.2405.06334 (2024)

  28. [34]

    Heesch, Zeitschrift f¨ ur Kristallographie-Crystalline Materials 73, 325 (1930)

    H. Heesch, Zeitschrift f¨ ur Kristallographie-Crystalline Materials 73, 325 (1930)

  29. [35]

    Tavger and V

    B. Tavger and V. Zaitsev, J. Exptl. Theoret. Phys. (USSR) 30, 564 (1956) [Sov. Phys. JETP 3, 430 (1956)] (1956)

  30. [36]

    Kitz, physica status solidi (b) 10, 455 (1965)

    A. Kitz, physica status solidi (b) 10, 455 (1965)

  31. [37]

    Brinkman and R

    W. Brinkman and R. Elliott, Journal of Applied Physics 37, 1457 (1966)

  32. [38]

    Brinkman and R

    W. Brinkman and R. J. Elliott, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences 294, 343 (1966)

  33. [39]

    D. B. Litvin and W. Opechowski, Physica 76, 538 (1974)

  34. [40]

    D. B. Litvin, Acta Crystallographica Section A: Crystal Physics, Diffraction, Theoretical and General Crystal- lography 33, 279 (1977)

  35. [41]

    P. Liu, J. Li, J. Han, X. Wan, and Q. Liu, Phys. Rev. X 12, 021016 (2022)

  36. [42]

    Jiang, Z

    Y. Jiang, Z. Song, T. Zhu, Z. Fang, H. Weng, Z.-X. Liu, J. Yang, and C. Fang, arXiv preprint arXiv:2307.10371 10.48550/arXiv.2307.10371 (2023)

  37. [43]

    J. Ren, X. Chen, Y. Zhu, Y. Yu, A. Zhang, J. Li, C. Li, and Q. Liu, arXiv preprint arXiv:2307.10369 10.48550/arXiv.2307.10369 (2023)

  38. [44]

    Z. Xiao, J. Zhao, Y. Li, R. Shindou, and Z.-D. Song, arXiv preprint arXiv:2307.10364 10.48550/arXiv.2307.10364 (2023)

  39. [45]

    Shinohara, A

    K. Shinohara, A. Togo, H. Watanabe, T. Nomoto, I. Tanaka, and R. Arita, Acta Crystallograph- ica Section A: Foundations and Advances 80, 10.1107/S2053273323009257 (2024)

  40. [46]

    Schiff, A

    H. Schiff, A. Corticelli, A. Guerreiro, J. Romh´ anyi, and P. McClarty, arXiv preprint arXiv:2307.12784 10.48550/arXiv.2307.12784 (2023)

  41. [47]

    Feng and Z

    X. Feng and Z. Zhang, arXiv preprint arXiv:2407.20504 10.48550/arXiv.2407.20504 (2024)

  42. [48]

    Keldysh, Zh

    L. Keldysh, Zh. Eksp. Teor. Phys. 47, 1515 (1964) [Sov. Phys. JETP 20, 1018 (1965)] (1965)

  43. [50]

    Kamenev and A

    A. Kamenev and A. Levchenko, Advances in Physics58, 197 (2009)

  44. [51]

    Kamenev, Field theory of non-equilibrium systems 19 (Cambridge University Press, 2023)

    A. Kamenev, Field theory of non-equilibrium systems 19 (Cambridge University Press, 2023)

  45. [52]

    M. V. Feigel’man, A. I. Larkin, and M. A. Skvortsov, Phys. Rev. B 61, 12361 (2000)

  46. [53]

    Efetov, Supersymmetry in disorder and chaos (Cam- bridge university press, 1999)

    K. Efetov, Supersymmetry in disorder and chaos (Cam- bridge university press, 1999)

  47. [54]

    Altland and B

    A. Altland and B. Simons, Condensed matter field the- ory (Cambridge university press, 2010)

  48. [55]

    Gurarie, Phys

    V. Gurarie, Phys. Rev. B 83, 085426 (2011)

  49. [56]

    Schwiete, Phys

    G. Schwiete, Phys. Rev. B 103, 125422 (2021)

  50. [57]

    Schwiete and A

    G. Schwiete and A. M. Finkel’stein, Phys. Rev. B 90, 060201 (2014)

  51. [58]

    Chamon, A

    C. Chamon, A. W. W. Ludwig, and C. Nayak, Phys. Rev. B 60, 2239 (1999)

  52. [59]

    Q. Yang, Y. Zuo, and D. E. Liu, Phys. Rev. Res. 5, 033174 (2023)

  53. [60]

    Altland and D

    A. Altland and D. Bagrets, Phys. Rev. Lett. 114, 257201 (2015)

  54. [61]

    Altland and D

    A. Altland and D. Bagrets, Phys. Rev. B 93, 075113 (2016)

  55. [62]

    Kamenev and A

    A. Kamenev and A. Andreev, Phys. Rev. B 60, 2218 (1999)

  56. [63]

    Y. Liao, A. Levchenko, and M. S. Foster, Annals of Physics 386, 97 (2017)

  57. [64]

    E. J. K¨ onig, A. Levchenko, I. V. Protopopov, I. V. Gornyi, I. S. Burmistrov, and A. D. Mirlin, Phys. Rev. B 92, 214503 (2015)

  58. [65]

    Feigel’man, A

    M. Feigel’man, A. Larkin, and M. Skvortsov, Pramana 64, 1039 (2005)

  59. [66]

    I. V. Yurkevich and I. V. Lerner, Phys. Rev. B 63, 064522 (2001)

  60. [67]

    Bulaevskii, A

    L. Bulaevskii, A. I. Buzdin, S. Panyukov, and M. Kuli´ c, Solid State Communications 44, 1247 (1982)

  61. [68]

    Radovi´ c, M

    Z. Radovi´ c, M. Ledvij, L. Dobrosavljevi´ c-Gruji´ c, A. I. Buzdin, and J. R. Clem, Phys. Rev. B 44, 759 (1991)

  62. [69]

    Lamacraft and B

    A. Lamacraft and B. D. Simons, Phys. Rev. Lett. 85, 4783 (2000)

  63. [70]

    Lamacraft and B

    A. Lamacraft and B. D. Simons, Phys. Rev. B 64, 014514 (2001)

  64. [71]

    F. M. Marchetti and B. Simons, Journal of Physics A: Mathematical and General 35, 4201 (2002)

  65. [72]

    Virtanen, A

    P. Virtanen, A. Vargunin, and M. Silaev, Phys. Rev. B 101, 094507 (2020)

  66. [73]

    Jedema, H

    F. Jedema, H. Heersche, A. Filip, J. Baselmans, and B. Van Wees, Nature 416, 713 (2002)

  67. [74]

    F. S. Bergeret, A. F. Volkov, and K. B. Efetov, Phys. Rev. Lett. 86, 4096 (2001)

  68. [75]

    A. A. Abrikosov, L. P. Gorkov, and I. E. Dzyaloshinski, Methods of quantum field theory in statistical physics (Pergamon press, 1965) English translation by D.E. Brown and D. Ter Haar

  69. [76]

    M. M. Vasiakin and A. S. Mel’nikov, Phys. Rev. B 111, L100502 (2025)

  70. [77]

    I. V. Bobkova, A. M. Bobkov, and M. A. Silaev, Phys. Rev. B 96, 094506 (2017)

  71. [78]

    Larkin and Y

    A. Larkin and Y. Ovchinnikov, Soviet Physics JETP41, 960 (1975)

  72. [79]

    Belzig, F

    W. Belzig, F. K. Wilhelm, C. Bruder, G. Sch¨ on, and A. D. Zaikin, Superlattices and microstructures 25, 1251 (1999)

  73. [80]

    F. S. Bergeret, M. Silaev, P. Virtanen, and T. T. Heikkil¨ a, Rev. Mod. Phys.90, 041001 (2018)

  74. [81]

    Tanaka, M

    Y. Tanaka, M. Sato, and N. Nagaosa, Journal of the Physical Society of Japan 81, 011013 (2011)

  75. [82]

    Houzet and A

    M. Houzet and A. I. Buzdin, Phys. Rev. B 76, 060504 (2007)

  76. [83]

    M. A. Silaev, I. V. Tokatly, and F. S. Bergeret, Phys. Rev. B 95, 184508 (2017)

  77. [84]

    Huang, I

    C. Huang, I. V. Tokatly, and M. A. Cazalilla, Phys. Rev. Lett. 127, 176801 (2021)

  78. [85]

    Cheong, J

    S. Cheong, J. D. Thompson, and Z. Fisk, Physica C: Superconductivity 158, 109 (1989)

  79. [86]

    Foo, W.-L

    M. Foo, W.-L. Lee, T. Siegrist, G. Lawes, A. Ramirez, N. Ong, and R. Cava, Materials research bulletin 39, 1663 (2004)

  80. [87]

    Kobayashi, Phys

    W. Kobayashi, Phys. Rev. B 79, 155116 (2009)

  81. [88]

    W. D. Ryden, A. W. Lawson, and C. C. Sartain, Phys. Rev. B 1, 1494 (1970)

  82. [89]

    Materials Project NaPr2OO6 https://next- gen.materialsproject.org/materials/mp-20009/, (2024)

  83. [90]

    Materials Project CoF3 https://next- gen.materialsproject.org/materials/mp-559435, (2024)

  84. [91]

    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, Phys. Rev. Lett. 126, 127701 (2021)

  85. [93]

    Kuprianov and V

    M. Kuprianov and V. Lukichev, Zh. Eksp. Teor. Fiz 94, 149 (1988)

  86. [94]

    Brinkman, M

    A. Brinkman, M. Huijben, M. Van Zalk, J. Huijben, U. Zeitler, J. Maan, W. G. van der Wiel, G. Rijnders, D. H. Blank, and H. Hilgenkamp, Nature materials 6, 493 (2007)

  87. [95]

    Hayami, Y

    S. Hayami, Y. Yanagi, and H. Kusunose, Phys. Rev. B 102, 144441 (2020)

  88. [96]

    Hayami, Y

    S. Hayami, Y. Yanagi, and H. Kusunose, Phys. Rev. B 101, 220403 (2020)

  89. [97]

    Hayami, Phys

    S. Hayami, Phys. Rev. B 105, 024413 (2022)

  90. [99]

    Vakili, E

    H. Vakili, E. Schwartz, and A. A. Kovalev, arXiv preprint arXiv:2412.11274 10.48550/arXiv.2412.11274 (2024)

  91. [100]

    Maeda, Y

    K. Maeda, Y. Fukaya, K. Yada, B. Lu, Y. Tanaka, and J. Cayao, arXiv preprint arXiv:2501.08646 10.48550/arXiv.2501.08646 (2025)

  92. [101]

    Sukhachov, H

    P. Sukhachov, H. G. Giil, B. Brekke, and J. Linder, arXiv preprint arXiv:2412.14245 10.48550/arXiv.2412.14245 (2024). 20 Appendix A: Construction of the effective action In this Appendix, we show how to construct the general action, Eq. (22) for collinear magnets, and Eq. (84)...

  93. [102]

    They are time-reversal odd and change sign upon reversal of all spins

    First order in exchange First we consider those terms up to first order in τ3σ and thus the tensor that is required is a vector in spin space. They are time-reversal odd and change sign upon reversal of all spins. a. Zeroth order in derivatives: Usual exchange term in ferromag...

  94. [103]

    Second order in exchange Next, we consider those terms that are second order in τ3σ. These terms, even though they can only be present if there are time-reversal symmetry breaking mechanisms in the materials, are themselves even in time-reversal, they do not change upon revers...

  95. [104]

    Here we show that Jj really describes the physical currents

    Matrix current from the vector potential Above, we have identified Jj as a matrix current. Here we show that Jj really describes the physical currents. To this end, we use that the physical currents, i.e. the charge and spin currents of the system, are obtained from − δS δA , ...

  96. [105]

    The first is 2m2m1m, which contains 3 independent mirror planes, the first two two of which need to be accompanied by a spin flip

    d - wave altermagnets There exist 4 collinear spin space groups with a d - wave altermagnet order parameter. The first is 2m2m1m, which contains 3 independent mirror planes, the first two two of which need to be accompanied by a spin flip. Thus, upon setting x − → −x or y − →y...

  97. [106]

    There exist 4 collinear spin space groups that allow for g - wave altermagnetism

    g - wave altermagnets Next, we consider the g - wave altermagnets. There exist 4 collinear spin space groups that allow for g - wave altermagnetism. The first group is 14/1m2m2m. The fourfold rotational symmetry around the z-axis, combined with the identity operator in spin sp...

  98. [107]

    There are two collinear spin space groups in which this type of altermagnetism may appear

    i - wave altermagnets Lastly, we consider the i - wave altermagnets. There are two collinear spin space groups in which this type of altermagnetism may appear. The first symmetry group is 16/1m2m2m. This group is invariant under six-fold rotations around the z-axis. In particu...

  99. [108]

    We impose a voltage ± V 2 at x = ± Lx 2 , while the spin-voltages vanish at those positions

    Infinite altermagnetic stripe: transverse voltage We first consider a 2D geometry that is infinite in the y-direction. We impose a voltage ± V 2 at x = ± Lx 2 , while the spin-voltages vanish at those positions. This fixes the boundary conditions µ(± L 2 ) = ± V 2 and µs z(± L...

  100. [109]

    We assume a constant electric field, along the x-direction

    Infinite altermagnetic stripe: electric field along the x-axis Next, we consider another simple setup: An infinite 2D stripe with boundaries at y = ±Ly/2. We assume a constant electric field, along the x-direction. By translational symmetry µs z does not depend on x, while µ =...

  101. [110]

    Combining the boundary conditions of the two previous problems, that is, using the boundary conditions in the x-direction used in Sec

    Finite system We now consider consider a rectangular altermagnet that is finite in both the x and y directions. Combining the boundary conditions of the two previous problems, that is, using the boundary conditions in the x-direction used in Sec. E 1 and the boundary condition...

  102. [111]

    The stripe is superconducting or proximitized by a bulk superconductor

    Altermagnetic stripe with superconducting correlations We consider an altermagnet stripe, which has a finite size in the y-direction, and an infinite size in the x direction. The stripe is superconducting or proximitized by a bulk superconductor. A supercurrent is flowing in t...

  103. [112]

    0 f ¯f 0 # , (F19) where f and ¯f are matrices in spin space that can be parameterized as f = f+ 0 0 f− , (F20) ¯f =

    T ransverse orientation We consider an altermagnet stripe, which has a finite size in the y-direction, and an infinite size in the x direction. The stripe is superconducting or proximitized by a bulk superconductor. A supercurrent is flowing in the x-direction, by imposing a p...

  104. [113]

    Junction geometry The above results are seemingly in contradiction with the results of Ref. [30], in which the authors claimed they one induces a spin accumulation at the transverse edges of a Josephson junction made by an altermagnet and two superconducting electrodes, that i...

  105. [114]

    The junction is infinite in the y direction

    Longitudinal effect First we consider a 2D junction between a superconductor (x <0) and altermagnet (x >0). The junction is infinite in the y direction. We assume that the lobe of the altermagnet is along the normal of the interface. In Fig. 2 this corresponds to panel a. In t...

  106. [115]

    In this case the reflection y − → −y changes the orientation of all spins, and therefore Kxx = 0 but Kxy ̸= 0

    T ransverse effect Next, we consider a similar setup, but now the lobes of the altermagnet are oriented in the transverse direction. In this case the reflection y − → −y changes the orientation of all spins, and therefore Kxx = 0 but Kxy ̸= 0. This happens if the normal to the...

  107. [116]

    In contrast, if the normal of the interface corresponds to a node direction of the altermagnet, there may only be a transverse effect

    Superconducting Island on top of an Altermagnet In the previous subsections we saw that if the normal of the interface corresponds to a lobe direction of the altermagnet, a magnetization is induced. In contrast, if the normal of the interface corresponds to a node direction of...

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Reviewed August 11, 2026 · model on record in the stance chip above.