Generalized continuum theory of phonon angular momentum in crystals
Pith reviewed 2026-05-10 16:27 UTC · model grok-4.3
The pith
A local SO(3) material frame determines the continuum phonon angular momentum density via Noether's theorem.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
We formulate a generalized continuum theory of phonon angular momentum in crystals by introducing a local SO(3) material frame in addition to the macroscopic displacement field. The local frame represents rotational optical degrees of freedom of the unit cell and brings acoustic displacement modes and optical rotational modes into a common long-wavelength continuum description. In the linearized limit, the co-rotated deformation gradient and the rotational gradient recover the Eringen microdeformation and wryness tensors; isotropic micropolar elasticity appears as a special case. Rotational symmetry and Noether's theorem determine the continuum phonon angular-momentum density, including both
What carries the argument
the local SO(3) material frame that represents rotational optical degrees of freedom of the unit cell and, together with the displacement field, yields the angular momentum density from Noether's theorem applied to rotational symmetry
Load-bearing premise
The local SO(3) material frame accurately represents the rotational optical degrees of freedom of the unit cell, and the linearized limit with co-rotated gradients recovers the Eringen tensors without additional corrections.
What would settle it
An experimental measurement of the phonon angular momentum or chiral splitting in a crystal that contradicts the predictions from the Noether-derived density or the identified symmetry-breaking terms would falsify the central claim.
Figures
read the original abstract
We formulate a generalized continuum theory of phonon angular momentum in crystals by introducing a local SO(3) material frame in addition to the macroscopic displacement field. The local frame represents rotational optical degrees of freedom of the unit cell and brings acoustic displacement modes and optical rotational modes into a common long-wavelength continuum description. In the linearized limit, the co-rotated deformation gradient and the rotational gradient associated with the local material frame recover the Eringen microdeformation and wryness tensors; isotropic micropolar elasticity then appears as a special case. Rotational symmetry and Noether's theorem determine the continuum phonon angular-momentum density, including both the displacement-polarization contribution and the intrinsic microrotation contribution. The theory further identifies the locking limit in which microrotation reduces to lattice vorticity and the improper-symmetry-breaking terms responsible for chiral phonon splitting.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper formulates a generalized continuum theory of phonon angular momentum in crystals by introducing a local SO(3) material frame in addition to the macroscopic displacement field. This frame is intended to represent rotational optical degrees of freedom of the unit cell, unifying acoustic displacement modes and optical rotational modes in a long-wavelength description. In the linearized limit the co-rotated deformation gradient and rotational gradient recover the Eringen microdeformation and wryness tensors, with isotropic micropolar elasticity appearing as a special case. Rotational symmetry and Noether's theorem are invoked to obtain the continuum phonon angular-momentum density (displacement-polarization plus intrinsic microrotation contributions). The theory further identifies a locking limit in which microrotation reduces to lattice vorticity and improper-symmetry-breaking terms that produce chiral phonon splitting.
Significance. If the central construction is validated, the work supplies a symmetry-derived continuum framework that places phonon angular momentum on a common footing with micropolar elasticity, potentially enabling parameter-free predictions of chiral-phonon effects and angular-momentum transport in crystals. The explicit use of Noether's theorem and the claimed recovery of established Eringen tensors constitute genuine strengths that could make the approach useful for both analytic and numerical studies in condensed-matter physics.
major comments (1)
- [Abstract and linearized-limit section] Abstract (and the linearized-limit derivation): the central claim that the co-rotated deformation gradient together with the rotational gradient of the local SO(3) frame recover the Eringen microdeformation and wryness tensors without additional lattice-scale corrections is load-bearing for the validity of the Noether-derived angular-momentum density and the predicted chiral-splitting terms. No explicit lattice-to-continuum matching calculation is supplied that starts from a discrete atomic model (where all degrees of freedom are displacements) and demonstrates that the independent microrotation field and its stiffness reproduce the long-wavelength limit of the lattice without extra corrections. This verification is required to confirm that the continuum angular-momentum density is not ambiguous.
minor comments (2)
- [Notation and definitions] Clarify the precise definition of the local SO(3) material frame (e.g., how its orientation is tied to the unit-cell basis vectors) and ensure that all subsequent expressions for the deformation gradient and wryness tensor are written in a notation that makes the reduction to Eringen tensors immediate.
- [Introduction] Add a short paragraph contrasting the present construction with existing micropolar or Cosserat continuum models of phonons to highlight what is genuinely new.
Simulated Author's Rebuttal
We thank the referee for the positive evaluation of our manuscript and for highlighting the importance of validating the continuum limit. We address the major comment in detail below.
read point-by-point responses
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Referee: [Abstract and linearized-limit section] Abstract (and the linearized-limit derivation): the central claim that the co-rotated deformation gradient together with the rotational gradient of the local SO(3) frame recover the Eringen microdeformation and wryness tensors without additional lattice-scale corrections is load-bearing for the validity of the Noether-derived angular-momentum density and the predicted chiral-splitting terms. No explicit lattice-to-continuum matching calculation is supplied that starts from a discrete atomic model (where all degrees of freedom are displacements) and demonstrates that the independent microrotation field and its stiffness reproduce the long-wavelength limit of the lattice without extra corrections. This verification is required to confirm that the continuum angular-momentum density is not ambiguous.
Authors: We agree that an explicit demonstration of the lattice-to-continuum limit would strengthen the foundation of our theory. In the current manuscript, the recovery of the Eringen tensors is shown through direct linearization of the kinematic fields defined by the local SO(3) frame and the displacement field, which by construction matches the micropolar kinematics. The Noether-derived angular momentum follows from the rotational invariance of the continuum Lagrangian. However, to rigorously address potential concerns about lattice-scale corrections, we will revise the manuscript by adding a new appendix that performs a lattice-to-continuum matching calculation using a simple one-dimensional diatomic chain model with rotational degrees of freedom. In this model, we will show that the independent microrotation field emerges in the long-wavelength limit and reproduces the continuum angular-momentum density without additional terms. This addition will confirm the absence of ambiguities. revision: yes
Circularity Check
No significant circularity; derivation grounded in Noether's theorem on introduced fields
full rationale
The paper introduces an independent local SO(3) material frame to encode unit-cell rotational optical modes alongside the macroscopic displacement field. It then applies standard rotational symmetry and Noether's theorem to obtain the angular-momentum density (both displacement-polarization and intrinsic microrotation terms). This step does not reduce by construction to a fitted parameter, a self-referential definition, or a load-bearing self-citation; the result follows directly from the symmetry principles once the fields are posited. The claim that the linearized co-rotated deformation gradient and rotational gradient recover the Eringen tensors is presented as an algebraic consequence of the construction rather than a prediction fitted to data. No evidence appears of ansatz smuggling, renaming of known results, or uniqueness theorems imported from the authors' prior work that would force the outcome. The derivation remains self-contained against external benchmarks such as micropolar elasticity.
Axiom & Free-Parameter Ledger
axioms (1)
- standard math Rotational symmetry and Noether's theorem determine the continuum phonon angular-momentum density
invented entities (1)
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local SO(3) material frame
no independent evidence
Lean theorems connected to this paper
-
IndisputableMonolith/Foundation/AlexanderDuality.leanalexander_duality_circle_linking unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We formulate a generalized continuum theory of phonon angular momentum in crystals by introducing a local SO(3) material frame in addition to the macroscopic displacement field. ... Rotational symmetry and Noether's theorem determine the continuum phonon angular-momentum density
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
Unified phonon angular momentum: The to- tal angular momentum follows from Noether’s the- orem as the sum of displacement polarization and intrinsic microrotation. This establishes a con- tinuum definition of phonon angular momentum, rather than only a change of variables in micropo- lar elasticity
-
[2]
V orticity in conservation laws: Lattice vortic- ity enters as a locking limit, ϕ ≈ ∇ × u/2, rather than as a fundamental field. The resulting conser- vation law reduces to the vorticity-driven form used for surface acoustic waves
-
[3]
Generalized continua and chirality: The same variables extend to micromorphic, microstretch, and micropolar continua, and they connect parity- breaking terms to the local frame
-
[4]
Phonon dispersion: The dispersion relations of acoustic and optical phonons can be obtained an- alytically. In the presence of a symmetry-allowed inversion- and mirror-symmetry-breaking term, the formulation captures chiral splitting of the phonon dispersion. C. Relation to earlier local-frame formulations We briefly recall earlier local-frame formulation...
-
[5]
L. Zhang and Q. Niu, Angular Momentum of Phonons and the Einstein-de Haas Effect, Phys. Rev. Lett. 112, 085503 (2014)
work page 2014
-
[6]
S. V. Vonsovskii and M. S. Svirskii, Chiral phonons and pseudoangular momentum in nonsymmorphic systems, Sov. Phys. Solid State 3, 1568 (1962)
work page 1962
-
[7]
A. G. McLellan, Angular momentum states for phonons and a rotationally invariant development of lattice dy- namics, J. Phys. C: Solid State Phys. 21, 1177 (1988)
work page 1988
-
[8]
D. A. Garanin and E. M. Chudnovsky, Angular momen- tum in spin-phonon processes, Phys. Rev. B 92, 024421 (2015)
work page 2015
-
[9]
J. J. Nakane and H. Kohno, Angular momentum of phonons and its application to single-spin relaxation, Phys. Rev. B 97, 174403 (2018)
work page 2018
-
[10]
A. Rückriegel, S. Streib, G. E. W. Bauer, and R. A. Duine, Angular momentum conservation and phonon spin in magnetic insulators, Phys. Rev. B 101, 104402 (2020)
work page 2020
- [11]
-
[12]
S. Park and B.-J. Yang, Phonon Angular Momentum Hall Effect, Nano Letters 20, 7694 (2020)
work page 2020
-
[13]
M. Hamada and S. Murakami, Phonon rotoelectric effect, Phys. Rev. B 101, 144306 (2020)
work page 2020
-
[14]
K. Ohe, H. Shishido, M. Kato, S. Utsumi, H. Matsuura, and Y. Togawa, Chirality-Induced Selectivity of Phonon Angular Momenta in Chiral Quartz Crystals, Phys. Rev. Lett. 132, 056302 (2024)
work page 2024
-
[15]
D. M. Juraschek, R. M. Geilhufe, H. Zhu, M. Basini, P. Baum, A. Baydin, S. Chaudhary, M. Fechner, B. Fle- bus, G. Grissonnanche, A. I. Kirilyuk, M. Lemeshko, S. F. Maehrlein, M. Mignolet, S. Murakami, Q. Niu, U. Nowak, C. P. Romao, H. Rostami, T. Satoh, N. A. 9 Spaldin, H. Ueda, and L. Zhang, Chiral phonons, Nat. Phys. 21, 1532 (2025)
work page 2025
-
[16]
F. Y. Hansen and H. L. McMurry, Normal mode cal- culations of trigonal selenium, J. Chem. Phys. 72, 5550 (1980)
work page 1980
-
[17]
H. Komiyama, T. Zhang, and S. Murakami, Physics of phonons in systems with approximate screw symmetry, Phys. Rev. B 106, 184104 (2022)
work page 2022
-
[18]
H. Tsunetsugu and H. Kusunose, Theory of Energy Dis- persion of Chiral Phonons, J. Phys. Soc. Jpn. 92, 023601 (2023)
work page 2023
-
[19]
A. Kato and J.-i. Kishine, Note on Angular Momentum of Phonons in Chiral Crystals, J. Phys. Soc. Jpn. 92, 075002 (2023)
work page 2023
-
[20]
H. Tsunetsugu and H. Kusunose, Chiral Phonons in a Cubic Lattice, J. Phys. Soc. Jpn. 95, 013601 (2026)
work page 2026
-
[21]
A. Einstein and W. J. de Haas, Experimental proof of the existence of ampère’s molecular currents, Verh. Dtsch. Phys. Ges. 17, 152 (1915)
work page 1915
-
[22]
S. J. Barnett, Magnetization by Rotation, Phys. Rev. 6, 239 (1915)
work page 1915
-
[23]
G. G. Scott, Review of Gyromagnetic Ratio Experiments, Rev. Mod. Phys. 34, 102 (1962)
work page 1962
- [24]
- [25]
-
[26]
T. M. Wallis, J. Moreland, and P. Kabos, Einstein–de Haas effect in a NiFe film deposited on a microcantilever, Appl. Phys. Lett. 89, 122502 (2006)
work page 2006
-
[27]
G. Zolfagharkhani, A. Gaidarzhy, P. Degiovanni, S. Ket- temann, P. Fulde, and P. Mohanty, Nanomechanical de- tection of itinerant electron spin flip, Nat. Nanotechnol. 3, 720 (2008)
work page 2008
-
[28]
M. Ono, H. Chudo, K. Harii, S. Okayasu, M. Matsuo, J. Ieda, R. Takahashi, S. Maekawa, and E. Saitoh, Phys. Rev. B 92, 174424 (2015)
work page 2015
- [29]
-
[30]
A. Hirohata, Y. Baba, B. A. Murphy, B. Ng, Y. Yao, K. Nagao, and J.-y. Kim, Magneto-optical detection of spin accumulation under the influence of mechanical ro- tation, Scientific reports 8, 1974 (2018)
work page 1974
-
[31]
M. Imai, Y. Ogata, H. Chudo, M. Ono, K. Harii, M. Mat- suo, Y. Ohnuma, S. Maekawa, and E. Saitoh, Obser- vation of gyromagnetic reversal, Appl. Phys. Lett. 113, 10.1063/1.5041464 (2018)
-
[32]
M. Imai, H. Chudo, M. Ono, K. Harii, M. Matsuo, Y. Ohnuma, S. Maekawa, and E. Saitoh, Angular mo- mentum compensation manipulation to room tempera- ture of the ferrimagnet ho3- xdyxfe5o12 detected by the barnett effect, Applied Physics Letters 114 (2019)
work page 2019
- [33]
- [34]
- [35]
- [36]
- [37]
- [38]
-
[39]
A. Wood, E. Lilette, Y. Fein, V. Perunicic, L. Hollenberg, R. Scholten, and A. Martin, Magnetic pseudo-fields in a rotating electron–nuclear spin system, Nat. Phys. 13, 1070 (2017)
work page 2017
-
[40]
A. A. Wood, E. Lilette, Y. Y. Fein, N. Tomek, L. P. McGuinness, L. C. L. Hollenberg, R. E. Scholten, and A. M. Martin, Quantum measurement of a rapidly rotat- ing spin qubit in diamond, Science Advances 4, eaar7691 (2018)
work page 2018
-
[41]
Y. Jin, K. Shen, P. Ju, X. Gao, C. Zu, A. J. Grine, and T. Li, Quantum control and Berry phase of electron spins in rotating levitated diamonds in high vacuum, Nature Communications 15, 5063 (2024)
work page 2024
-
[42]
D. Kobayashi, T. Yoshikawa, M. Matsuo, R. Iguchi, S. Maekawa, E. Saitoh, and Y. Nozaki, Spin Current Generation Using a Surface Acoustic Wave Generated via Spin-Rotation Coupling, Phys. Rev. Lett. 119, 077202 (2017)
work page 2017
-
[43]
Y. Kurimune, M. Matsuo, S. Maekawa, and Y. Nozaki, Phys. Rev. B 102, 174413 (2020)
work page 2020
-
[44]
Y. Kurimune, M. Matsuo, and Y. Nozaki, Phys. Rev. Lett. 124, 217205 (2020)
work page 2020
- [45]
- [46]
-
[47]
K. Harii, Y.-J. Seo, Y. Tsutsumi, H. Chudo, K. Oy- anagi, M. Matsuo, Y. Shiomi, T. Ono, S. Maekawa, and E. Saitoh, Spin Seebeck mechanical force, Nat. Commun. 10, 2616 (2019)
work page 2019
-
[48]
K. Mori, M. G. Dunsmore, J. E. Losby, D. M. Jenson, M. Belov, and M. R. Freeman, Einstein–de Haas effect at radio frequencies in and near magnetic equilibrium, Phys. Rev. B 102, 054415 (2020)
work page 2020
- [49]
-
[50]
T. Horaguchi, C. He, Z. Wen, H. Nakayama, T. Ohkubo, S. Mitani, H. Sukegawa, J. Fujimoto, K. Yamanoi, M. Matsuo, et al. , Nanometer-thick si/al gradient ma- terials for spin torque generation, Science Advances 11, eadr9481 (2025)
work page 2025
-
[51]
R. Takahashi, M. Matsuo, M. Ono, K. Harii, H. Chudo, S. Okayasu, J. Ieda, S. Takahashi, S. Maekawa, and E. Saitoh, Nature Phys 12, 52 (2016)
work page 2016
-
[52]
R. Takahashi, H. Chudo, M. Matsuo, K. Harii, Y. Ohnuma, S. Maekawa, and E. Saitoh, Nat Commun 11, 3009 (2020)
work page 2020
-
[53]
H. Tabaei Kazerooni, A. Thieme, J. Schumacher, and C. Cierpka, Phys. Rev. Applied 14, 014002 (2020)
work page 2020
-
[54]
H. Tabaei Kazerooni, G. Zinchenko, J. Schumacher, and C. Cierpka, Phys. Rev. Fluids 6, 043703 (2021)
work page 2021
-
[55]
M. Tokoro and R. Takahashi, Spin hydrodynamic gener- ation in low-melting-point pure metal, Physical Review Applied 17, L061003 (2022). 10
work page 2022
-
[56]
L. Adamczyk, J. Adkins, G. Agakishiev, M. Aggarwal, Z. Ahammed, N. Ajitanand, I. Alekseev, D. Anderson, R. Aoyama, A. Aparin, et al. , Global λ hyperon polar- ization in nuclear collisions, Nature 548 (2017)
work page 2017
-
[57]
J. Adam, L. Adamczyk, J. R. Adams, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, D. M. Anderson, et al. (STAR Collaboration), Global polarization of Λ hyperons in Au + Au collisions at √sN N = 200 GeV, Phys. Rev. C 98, 014910 (2018)
work page 2018
-
[58]
J. Adam, L. Adamczyk, J. R. Adams, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alek- seev, D. M. Anderson, R. Aoyama, et al. (STAR Collab- oration), Polarization of Λ (Λ) Hyperons along the Beam Direction in Au + Au Collisions at √sN N = 200 GeV , Phys. Rev. Lett. 123, 132301 (2019)
work page 2019
-
[59]
S. Acharya, D. Adamová, A. Adler, J. Adolfsson, M. M. Aggarwal, G. Aglieri Rinella, M. Agnello, N. Agrawal, Z. Ahammed, S. Ahmad, et al. (The ALICE Collabo- ration), Evidence of Spin-Orbital Angular Momentum Interactions in Relativistic Heavy-Ion Collisions, Phys. Rev. Lett. 125, 012301 (2020)
work page 2020
-
[60]
J. Adam, L. Adamczyk, J. R. Adams, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alek- seev, D. M. Anderson, A. Aparin, et al. (STAR Collab- oration), Global Polarization of Ξ and Ω Hyperons in Au + Au Collisions at √sN N = 200 GeV , Phys. Rev. Lett. 126, 162301 (2021)
work page 2021
- [61]
-
[62]
A. C. Eringen, Microcontinuum Field Theories. I: Foun- dations and Solids (Springer, New York, 1999)
work page 1999
- [63]
- [64]
-
[65]
J. Kishine, A. S. Ovchinnikov, and A. A. Tereshchenko, Chirality-induced phonon dispersion in a noncentrosym- metric micropolar crystal, Phys. Rev. Lett. 125, 245302 (2020)
work page 2020
-
[66]
L. D. Landau, E. M. Lifshitz, A. M. Kosevich, and L. P. Pitaevskii, Theory of Elasticity , 3rd ed. (Elsevier / Butterworth–Heinemann, Amsterdam, The Netherlands, 1986)
work page 1986
-
[67]
E. Cosserat and F. Cosserat, Théorie des corps dé- formables (Hermann, Paris, 1909)
work page 1909
-
[68]
A. C. Eringen, Linear theory of micropolar elasticity, Journal of Mathematics and Mechanics 15, 909 (1966)
work page 1966
-
[69]
Nowacki, Theory of Asymmetric Elasticity (Perga- mon Press, 1985)
W. Nowacki, Theory of Asymmetric Elasticity (Perga- mon Press, 1985)
work page 1985
-
[70]
F. W. Hehl, P. von der Heyde, G. D. Kerlick, and J. M. Nester, General relativity with spin and torsion: Foun- dations and prospects, Reviews of Modern Physics 48, 393 (1976)
work page 1976
-
[71]
Kleinert, Gauge Fields in Condensed Matter , Vol
H. Kleinert, Gauge Fields in Condensed Matter , Vol. II: Stresses and Defects (World Scientific, Singapore, 1989)
work page 1989
-
[72]
D. C. Lagoudas, A gauge theory for defects in media with microstructure, International Journal of Engineering Sci- ence 27, 1229 (1989)
work page 1989
-
[73]
M. Lazar, The gauge theory of dislocations: a non- singular screw dislocation, Philosophical Magazine 89, 199 (2009)
work page 2009
-
[74]
M. Lazar, On the Higgs mechanism and stress functions in the translational gauge theory of dislocations, Physics Letters A 373, 1578 (2009)
work page 2009
-
[75]
F. Gay-Balmaz and T. S. Ratiu, The geometric struc- ture of complex fluids and eringen’s theory, Advances in Applied Mathematics 45, 335 (2010)
work page 2010
-
[76]
P. Neff, I.-D. Ghiba, M. Lazar, and A. Madeo, The re- laxed linear micromorphic continuum: well-posedness of the static problem and relations to the gauge theory of dislocations, Quarterly Journal of Mechanics and Applied Mathematics 68, 53 (2015)
work page 2015
-
[77]
C. G. Böhmer and Y. N. Obukhov, A gauge-theoretic approach to elasticity with microrotations, Proceedings of the Royal Society A 468, 1391 (2012)
work page 2012
-
[78]
Here the rotation acts on the physical spatial orienta- tion of both the macroscopic body and the local material frame attached to the microstructure. This physical ro- tation differs from a mere relabeling of material-frame components, which would change the local basis used to describe the same physical configuration. The present for- mulation uses Q as...
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[79]
The second term in Eq. ( 46) arises from the decomposi- tion y = x+u in the linearized regime, and it is useful to keep it explicit when comparing different conventions in the phonon angular momentum literature. The microro- tation contribution is expressed as IΩ, with components Ωk = −εabk(Q−1∂tQ)ab/2 in the convention used here. The replacement Ω ≃ ˙ϕ c...
-
[80]
( 57) is the bulk representative of a chiral micropolar coupling
The term in Eq. ( 57) is the bulk representative of a chiral micropolar coupling. Indeed, ϕ·(∇×ϕ) = ϵijγij −ϵiiγkk − ∂i(uj∂jϕi−ui∂jϕj), which is equivalent, modulo a surface term, to Cijkl ϵijγkl with Cijkl = (χ/2)(δikδjl − δijδkl)
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