Topical Review on Skyrmions and Hall Transport
Pith reviewed 2026-05-24 20:02 UTC · model grok-4.3
The pith
Broken parity symmetry in Skyrmion systems requires Hall viscosity as an antisymmetric viscosity component.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Broken parity symmetry in the effective field theory of Skyrmions implies, via the quantum field theory Ward identity, the existence of Hall viscosity as an antisymmetric component of the viscosity tensor; this term is measurable through the momentum dependence of the Hall conductivity.
What carries the argument
Quantum field theory Ward identity applied to Skyrmion effective theories with broken parity symmetry.
If this is right
- Hall viscosity must accompany electric and thermal Hall conductivities in any parity-broken Skyrmion system.
- Momentum dependence of Hall conductivity provides a direct experimental probe of Hall viscosity.
- The Ward-identity result holds for both insulating and conducting magnets.
- Spin-torque and thermo-electromagnetic descriptions remain compatible with the symmetry-derived viscosity term.
Where Pith is reading between the lines
- The same Ward-identity logic may apply to other topological textures that break parity, such as merons or domain walls.
- Momentum-resolved transport experiments on thin-film Skyrmion lattices could isolate the viscosity coefficient.
- If Hall viscosity is confirmed, it supplies an additional hydrodynamic variable for modeling Skyrmion dynamics at long wavelengths.
Load-bearing premise
The Ward identity analysis assumes that the symmetries and conservation laws of the effective field theory directly produce a new independent transport coefficient without cancellations from microscopic dynamics.
What would settle it
A momentum-resolved Hall conductivity measurement that exhibits no antisymmetric viscosity contribution, or a microscopic Skyrmion calculation that cancels the predicted term.
Figures
read the original abstract
We review recent progresses towards an understanding of the Skyrmion Hall transport in insulating as well as conducting materials. First, we consider a theoretical breakthrough based on the quantum field theory Ward identity, a first principle analysis, relying on symmetries and conservation laws. Broken parity (inversion) symmetry plays a crucial role in Skyrmion Hall transport. In addition to the well known thermal and electric Hall conductivities, our analysis has led us to the discovery of a new and unforeseen physical quantity, Hall viscosity - an anti-symmetric part of the viscosity tensor. We propose a simple way to confirm the existence of Hall viscosity in the measurements of Hall conductivity as a function of momentum. We provide various background materials to assist the readers to understand the quantum field theory Ward identity. In the second part, we review recent theoretical and experimental advancements of the Skyrmion Hall effects and the topological (Magnon) Hall effects for conducting (insulting) magnets. For this purpose, we consider two enveloping themes: spin torque and thermo-electromagnetic effect. First, we overview various spin torques, such as spin transfer torque, spin-orbit torque, and spin Hall torque, and generalized Landau-Lifshitz-Gilbert equations and Thiele equations using a phenomenological approach. Second, we consider irreversible thermodynamics to survey possible thermo-electromagnetic effects, such as Seebeck, Peltier and Thompson effects in the presence of the electric currents, along with the Hall effects in the presence of a background magnetic field. Recently developed spin Seebeck effects are also a significant part of the survey. We also accommodate extensive background materials to make this review self-contained. Finally, we revisit the Skyrmion Hall transport from the Ward identity view point.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This topical review covers Skyrmion Hall transport in insulating and conducting magnets. The central claim is that broken parity symmetry, analyzed via quantum field theory Ward identities relying on symmetries and conservation laws, implies the existence of a new independent transport coefficient—Hall viscosity, the antisymmetric component of the viscosity tensor—in addition to known thermal and electric Hall conductivities; this is proposed to be measurable via momentum dependence of the Hall conductivity. The second part surveys spin torques (including spin-transfer, spin-orbit, and spin-Hall torques), generalized LLG and Thiele equations, thermo-electromagnetic effects (Seebeck, Peltier, spin Seebeck), and revisits Skyrmion Hall transport, with extensive background material provided throughout.
Significance. If the Ward-identity derivation rigorously establishes an independent Hall viscosity without absorption into existing coefficients or cancellation by Skyrmion-specific dynamics, the result would add a falsifiable, first-principles transport coefficient to the literature on parity-broken topological magnets. The review's self-contained background sections on Ward identities, spin torques, and irreversible thermodynamics are a clear strength for accessibility.
major comments (2)
- [Ward identity / theoretical breakthrough section] Section on the Ward-identity analysis (theoretical breakthrough part): the claim that broken parity plus conservation laws directly produces an independent Hall viscosity does not address whether Skyrmion-specific features (topological charge, spin texture, or lattice effects) could induce cancellations that force the antisymmetric viscosity coefficient to zero or absorb it into the symmetric viscosity or Hall-conductivity terms already present in the EFT.
- [Measurement proposal paragraph] Proposal for experimental confirmation via momentum-dependent Hall conductivity: the manuscript does not supply the explicit relation (or error estimate) connecting the Hall-viscosity coefficient to the measurable momentum dependence, leaving open whether the predicted signature is distinguishable from ordinary dispersive corrections already present in the conductivity tensor.
minor comments (2)
- [Abstract] Abstract: 'insulting magnets' is a typographical error and should read 'insulating magnets'.
- [Theoretical background] Notation for the viscosity tensor and its antisymmetric component is introduced without an explicit equation defining the decomposition; adding this would improve clarity for readers unfamiliar with the Hall-viscosity literature.
Simulated Author's Rebuttal
We thank the referee for the detailed and constructive report on our topical review. The comments highlight important points for clarification regarding the generality of the Ward-identity derivation and the experimental proposal. We address each major comment below and indicate the revisions we will make.
read point-by-point responses
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Referee: Section on the Ward-identity analysis (theoretical breakthrough part): the claim that broken parity plus conservation laws directly produces an independent Hall viscosity does not address whether Skyrmion-specific features (topological charge, spin texture, or lattice effects) could induce cancellations that force the antisymmetric viscosity coefficient to zero or absorb it into the symmetric viscosity or Hall-conductivity terms already present in the EFT.
Authors: The Ward identities follow directly from the symmetries and conservation laws assumed in the effective theory for parity-broken magnets; these are general and independent of the specific microscopic realization. Skyrmion topological charge and spin texture enter the EFT parameters but do not modify the tensor structure of the allowed transport coefficients. The antisymmetric viscosity coefficient remains independent under the stated assumptions and is not absorbed into symmetric viscosity or Hall conductivity terms. To make this explicit, we will add a clarifying paragraph in the revised manuscript discussing why Skyrmion-specific features do not induce the cancellations suggested. revision: yes
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Referee: Proposal for experimental confirmation via momentum-dependent Hall conductivity: the manuscript does not supply the explicit relation (or error estimate) connecting the Hall-viscosity coefficient to the measurable momentum dependence, leaving open whether the predicted signature is distinguishable from ordinary dispersive corrections already present in the conductivity tensor.
Authors: We agree that an explicit relation would improve the proposal. In the revision we will supply the leading-order relation between the Hall-viscosity coefficient and the momentum dependence of the Hall conductivity, derived from the hydrodynamic expansion, together with a brief discussion of the momentum scales at which the Hall-viscosity signature can be distinguished from ordinary dispersive corrections, including a rough error estimate based on typical material parameters. revision: yes
Circularity Check
Ward identity derivation of Hall viscosity stands as independent first-principles result
full rationale
The paper frames Hall viscosity as a new quantity emerging directly from broken parity symmetry via quantum field theory Ward identities applied to the Skyrmion effective theory, relying on standard conservation laws and symmetries rather than any fitted parameters, self-defined relations, or load-bearing self-citations that reduce the claim to its own inputs. No equations or steps in the provided abstract or description exhibit a prediction that collapses by construction to a prior fit or renaming; the analysis is presented as additive to existing Hall conductivities and is supported by background QFT materials. The review structure incorporates external advancements in spin torques and thermo-electromagnetic effects without circular reduction in the central claim.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Quantum field theory Ward identities apply directly to the effective description of Skyrmion transport
invented entities (1)
-
Hall viscosity
no independent evidence
Reference graph
Works this paper leans on
-
[1]
Mühlbauer et al., Skyrmion lattice in a chiral magnet
S. Mühlbauer et al., Skyrmion lattice in a chiral magnet. Science 323, 915 (2009)
work page 2009
-
[2]
X. Z. Yu et al., Real-space observation of a two-dimensional skyrmion crystal. Nature 465, 901 (2010)
work page 2010
-
[3]
Jonietz et al., Spin transfer torque in MnSi at ultralow current densities
F. Jonietz et al., Spin transfer torque in MnSi at ultralow current densities. Science 330, 1648 (2010). 61 of 66
work page 2010
-
[4]
Heinze et al., Spontaneous atomic-scale magnetic skyrmion lattice in two dimensions
S. Heinze et al., Spontaneous atomic-scale magnetic skyrmion lattice in two dimensions. Nature Phys. 7, 713 (2011)
work page 2011
- [5]
-
[6]
A. N. Bogdanov, U. K. Rössler, M. Wolf, and K.-H. Müller, Magnetic structures and reorientation transitions in noncentrosymmetric uniaxial antiferromagnets. Phys. Rev. B 66, 214410 (2002)
work page 2002
-
[7]
U. Rössler, A. Bogdanov, and C. Pfleiderer, Spontaneous skyrmion ground states in magnetic metals. Nature (London) 442, 797 (2006)
work page 2006
-
[8]
B. Binz, A. Vishwanath, and V . Aji, Theory of the Helical Spin Crystal: A Candidate for the Partially Ordered State of MnSi. Phys. Rev. Lett. 96, 207202 (2006)
work page 2006
-
[9]
B. Binz and A. Vishwanath, Theory of helical spin crystals: Phases, textures, and properties. Phys. Rev. B 74, 214408 (2006)
work page 2006
- [10]
-
[11]
I. Fischer, N. Shah, and A. Rosch, Crystalline phases in chiral ferromagnets: Destabilization of helical order. Phys. Rev. B 77, 024415 (2008)
work page 2008
-
[12]
Jensen et al., Parity-Violating Hydrodynamics in 2+1 Dimensions
K. Jensen et al., Parity-Violating Hydrodynamics in 2+1 Dimensions. JHEP 1205, 102 (2012)
work page 2012
-
[13]
J. Bhattacharya, S. Bhattacharyya, S. Minwalla and A. Yarom, A Theory of first order dissipative superfluid dynamics. JHEP 1405, 147 (2014)
work page 2014
- [14]
-
[15]
J. E. Avron, R. Seiler and P . G. Zograf, Viscosity of Quantum Hall Fluids. Phys. Rev. Lett. 75, 697 (1995)
work page 1995
-
[16]
N. Read, Non-Abelian adiabatic statistics and Hall viscosity in quantum Hall states and p(x) + ip (y) paired superfluids. Phys. Rev. B 79, 045308 (2009)
work page 2009
-
[17]
N. Read and E. H. Rezayi, Hall viscosity, orbital spin, and geometry: paired superfluids and quantum Hall systems. Phys. Rev. B 84, 085316 (2011)
work page 2011
-
[18]
C. Hoyos and D. T. Son, Hall Viscosity and Electromagnetic Response. Phys. Rev. Lett. 108, 066805 (2012)
work page 2012
-
[19]
B. Bradlyn, M. Goldstein and N. Read, Kubo formulas for viscosity: Hall viscosity, Ward identities, and the relation with conductivity. Phys. Rev. B86, 245309 (2012)
work page 2012
- [20]
- [21]
-
[22]
H. B. Callen, The Application of Onsager’s Reciprocal Relations to Thermoelectric, Thei omagnetic, and Galvanomagnetic Effects. Phys. Rev. 73, 1349 (1948)
work page 1948
-
[23]
H. B. Callen, Thermodynamics: An introduction to the physical theories of equilibrium thermostatics and irreversible thermodynamics. John Wiley and Sons, Inc., 1960
work page 1960
- [24]
-
[25]
K. Litzius et. al., Skyrmion Hall effect revealed by direct time-resolved X-ray microscopy. Nature Physics 13, 170 (2017)
work page 2017
-
[26]
B. S. Kim and A. D. Shapere, Skyrmions and Hall Transport. Phys. Rev. Lett. 117, 116805 (2016)
work page 2016
-
[27]
H. Watanabe and H. Murayama, Noncommuting Momenta of Topological Solitons. Phys. Rev. Lett. 112, 191804 (2014)
work page 2014
-
[28]
N. Papanicolaou and T. N. Tomaras, Dynamics of Magnetic Vortices. Nucl. Phys. B 360, 425 (1991)
work page 1991
-
[29]
B. S. Kim, Skyrmions and Hall viscosity. AIP Adv. 8, 055601 (2017)
work page 2017
- [30]
-
[31]
S. Coleman and R. Jackiw, Why dilatation generators do not generate dilatations. Annals of Physics, 67, 552 (1971)
work page 1971
-
[32]
R. Jackiw and N. S. Manton, Symmetries and conservation laws in gauge theories. Annals of Physics, 127, 257 (1980)
work page 1980
-
[33]
F. J. Belinfante, On the spin angular momentum of mesons. Physica, 6, 887 (1939)
work page 1939
- [34]
-
[35]
L. D. Landau and E. M. Lifshitz, Fluid Mechanics, Third Impression. Pergamon Press Ltd. (1966)
work page 1966
-
[36]
L. D. Landau and E. M. Lifshitz, Theory of Elasticity, 3rd Edition. Pergamon Press, Oxford (1986). 62 of 66
work page 1986
-
[37]
T. L. Hughes, R. G. Leigh, and O. Parrikar, Torsional anomalies, Hall viscosity, and bulk-boundary correspondence in topological states. Phys. Rev. D 88, 025040 (2013)
work page 2013
-
[38]
H. Liu, H. Ooguri, B. Stoica and N. Yunes, Spontaneous Generation of Angular Momentum in Holographic Theories. Phys. Rev. Lett. 110, 211601 (2013)
work page 2013
-
[39]
Levay, Berry phases for Landau Hamiltonians on deformed tori
P . Levay, Berry phases for Landau Hamiltonians on deformed tori. J. Math. Phys. 36, 2792 (1995)
work page 1995
-
[40]
I. V . Tokatly and G. Vignale, Lorentz shear modulus of a two-dimensional electron gas at high magnetic field. Phys. Rev. B 76, 161305(R) (2007)
work page 2007
-
[41]
I. V . Tokatly and G. Vignale, Lorentz shear modulus of fractional quantum Hall states. J. Phys: Condensed Matter, 21, 275603 (2009)
work page 2009
-
[42]
X. G. Wen and A. Zee, Shift and spin vector: New topological quantum numbers for the Hall fluids. Phys. Rev. Lett. 69, 953 (1992)
work page 1992
-
[43]
F. D. M. Haldane, Hall viscosity’ and intrinsic metric of incompressible fractional Hall fluids. arXiv:0906.1854 [cond-mat.str-el]
work page internal anchor Pith review Pith/arXiv arXiv
-
[44]
Y. J. Park and F. D. M. Haldane, Guiding-center Hall viscosity and intrinsic dipole moment along edges of incompressible fractional quantum Hall fluids. Phys. Rev. B 90, 045123 (2014)
work page 2014
-
[45]
M. F. Lapa and T. L. Hughes, Hall viscosity and geometric response in the Chern-Simons matrix model of the Laughlin states. Phys. Rev. B 97, 205122 (2018)
work page 2018
-
[46]
M. F. Lapa, C. Turner, T. L. Hughes and D. Tong, Hall Viscosity in the Non-Abelian Quantum Hall Matrix Model. Phys. Rev. B 98, 075133 (2018)
work page 2018
-
[47]
O. Saremi and D. T. Son, Hall viscosity from gauge/gravity duality. JHEP 1204, 091 (2012)
work page 2012
-
[48]
Weinberg, The Quantum Theory of Fields, Vol
S. Weinberg, The Quantum Theory of Fields, Vol. I. Cambridge University Press, Cambridge, England, 1995
work page 1995
-
[49]
N. Nagaosa and Y. Tokura, Topological properties and dynamics of magnetic skyrmions. Nature Nanotechnology, 8, 899 (2013)
work page 2013
-
[50]
J. Iwasaki, M. Mochizuki and N. Nagaosa, Universal current-velocity relation of skyrmion motion in chiral magnets. Nature Communications, 4, 1463 (2013)
work page 2013
-
[51]
S. A. Hartnoll and C. P . Herzog, Ohm’s Law at strong coupling: S duality and the cyclotron resonance. Phys. Rev. D 76, 106012 (2007)
work page 2007
-
[52]
S. A. Hartnoll and P . Kovtun, Hall conductivity from dyonic black holes. Phys. Rev. D 76, 066001 (2007)
work page 2007
-
[53]
Lee et al., Unusual Hall anomaly in MnSi under pressure
M. Lee et al., Unusual Hall anomaly in MnSi under pressure. Phys. Rev. Lett. 102, 186601 (2009)
work page 2009
-
[54]
Neubauer et al., Topological Hall effect in the A phase of MnSi
A. Neubauer et al., Topological Hall effect in the A phase of MnSi. Phys. Rev. Lett. 102, 186602 (2009)
work page 2009
-
[55]
Schulz et al., Emergent electrodynamics of skyrmions in a chiral magnet
T. Schulz et al., Emergent electrodynamics of skyrmions in a chiral magnet. Nature Physics, 8, 301 (2012)
work page 2012
-
[56]
Zang et al., Dynamics of Skyrmion Crystals in Metallic Thin Films
J. Zang et al., Dynamics of Skyrmion Crystals in Metallic Thin Films. Phys. Rev. Lett. 107, 136804 (2011)
work page 2011
-
[57]
Kanazawa et al., Large topological Hall effect in a short-period helimagnet MnGe
N. Kanazawa et al., Large topological Hall effect in a short-period helimagnet MnGe. Phys. Rev. Lett. 106, 156603 (2011)
work page 2011
-
[58]
Yufan Li, Y. et al. Robust formation of skyrmions and topological Hall effect anomaly in epitaxial thin films of MnSi. Phys. Rev. Lett. 110, 117202 (2013)
work page 2013
-
[59]
S. Seki, X. Z. Yu, S. Ishiwata and Y. Tokura, Observation of Skyrmions in a Multiferroic Material. Science336, 198 (2012)
work page 2012
-
[60]
M. Mochizuki et al., Thermally driven ratchet motion of a skyrmion microcrystal and topological magnon Hall effect. Nature Materials, 13, 241 (2014)
work page 2014
-
[61]
Seki et al., Formation and rotation of skyrmion crystal in the chiral-lattice insulator Cu2OSeO3
S. Seki et al., Formation and rotation of skyrmion crystal in the chiral-lattice insulator Cu2OSeO3. Phys. Rev. B 85, 220406(R) (2012)
work page 2012
-
[62]
G. E. W. Bauer, E. Saitoh and B. J. van Wees, Spin caloritronics. Nature Materials, 11, 391 (2012)
work page 2012
-
[63]
Finocchio et al., Magnetic skyrmions: from fundamental to applications
G. Finocchio et al., Magnetic skyrmions: from fundamental to applications. J. Phys. D: Appl. Phys., 49, 423001 (2016)
work page 2016
-
[64]
J. H. Han and H. Lee, Spin Chirality and Hall-Like Transport Phenomena of Spin Excitations. J. Phys. Soc. Jpn. 86, 011007 (2017)
work page 2017
-
[65]
A. Fert, N. Reyren and V . Cros, Magnetic skyrmions: advances in physics and potential applications. Nature Reviews Materials 2, 17031 (2017)
work page 2017
- [66]
-
[67]
Jiang et al, Skyrmions in magnetic multilayers
W. Jiang et al, Skyrmions in magnetic multilayers. Physics Reports, 704, 1 (2017)
work page 2017
-
[68]
H. Ochoa and Y. Tserkovnyak, Colloquium: Quantum skyrmionics. arXiv:1807.02203 [cond-mat.mes-hall]. 63 of 66
-
[69]
L. D. Landau and E. M. Lifshitz, Electrodynamics of Continuous Media. Pergamon Press LTD, 1984
work page 1984
-
[70]
L. D. Landau and E. M. Lifshitz, On the theory of the dispersion of magnetic permeability in ferromagnetic bodies. Physik. Zeits. Sowjetunion 8, 153-169 (1935)
work page 1935
-
[71]
T. L. Gilbert, A phenomenological theory of damping in ferromagnetic materials. IEEE Trans. Magn. 40, 3443 (2004)
work page 2004
-
[72]
Emori et al., Current-driven dynamics of chiral ferromagnetic domain walls
S. Emori et al., Current-driven dynamics of chiral ferromagnetic domain walls. Nature Materials 12, 611 (2013)
work page 2013
-
[73]
M. N. Baibich et al., Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices. Phys. Rev. Lett. 61, 2472 (1988)
work page 1988
-
[74]
M. Johnson and R. H. Silsbee, Thermodynamic analysis of interfacial transport and of the thermomagnetoelectric system. Phys. Rev. B 35, 4959 (1987)
work page 1987
-
[75]
T. Valet and A. Fert, Theory of the perpendicular magnetoresistance in magnetic multilayers. Phys. Rev. B 48, 7099 (1993)
work page 1993
-
[76]
S. Zhang and Z. Li, Roles of Nonequilibrium Conduction Electrons on the Magnetization Dynamics of Ferromagnets. Phys. Rev. Lett. 93, 127204 (2004)
work page 2004
-
[77]
A. Thiaville, Y. Nakatani, J. Miltat, Y Suzuki, Micromagnetic understanding of current-driven domain wall motion in patterned nanowires. Europhys. Lett. 69, 990 (2005)
work page 2005
-
[78]
G. S. D. Beach, M. Tsoi and J. L. Erskine, Current-induced domain wall motion. J. Magn. Magn. Mater. 320, 1272 (2008)
work page 2008
-
[79]
A. Manchon and S. Zhang, Theory of nonequilibrium intrinsic spin torque in a single nanomagnet. Phys. Rev. B 78, 212405 (2008)
work page 2008
-
[80]
Dresselhaus, Spin–orbit coupling effects in zinc blende structures
G. Dresselhaus, Spin–orbit coupling effects in zinc blende structures. Phys. Rev. 100, 580 (1955)
work page 1955
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