Signatures of three-state Potts nematicity in spin excitations of the van der Waals antiferromagnet FePSe₃
Pith reviewed 2026-05-18 19:44 UTC · model grok-4.3
The pith
Spin excitations in FePSe3 retain broken threefold symmetry slightly above the zigzag antiferromagnetic ordering temperature.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
In the antiferromagnetically ordered state, application of approximately 0.6 percent tensile strain suppresses one zigzag domain and promotes the other two, which lowers the symmetry of the antiferromagnetic order and the spin waves to C2. The broken C3 symmetry observed in the spin excitations persists slightly above TN approximately 108.6 K, even though the zigzag antiferromagnetic order has disappeared. These measurements supply direct evidence of magnetoelastic coupling and imply that the three-state Potts nematicity detected in the paramagnetic spin excitations originates from the vestigial order associated with the low-temperature zigzag antiferromagnetic order.
What carries the argument
Uniaxial-strain-induced selection among zigzag domains that produces a persistent C2 symmetry in the spin excitations above the Néel temperature, detected by neutron scattering.
If this is right
- Strain provides a practical handle for selecting specific zigzag domains and thereby controlling the symmetry of spin waves in FePSe3.
- Magnetoelastic coupling transmits the symmetry breaking of the low-temperature order into the paramagnetic regime.
- The three-state Potts nematicity is not an independent electronic phase but a vestigial consequence of the zigzag antiferromagnetic order.
- Similar domain-selection and symmetry-persistence effects are expected in other honeycomb-lattice van der Waals antiferromagnets under strain.
Where Pith is reading between the lines
- The same vestigial-order mechanism could account for nematic signatures seen in other two-dimensional magnets that lack obvious electronic driving forces.
- Experiments that apply strain only in the paramagnetic phase could test whether the nematic response requires proximity to the ordered state.
- The results suggest that elastic control of spin excitations may be feasible in related materials for potential spintronic or magnonic applications.
Load-bearing premise
The observed persistence of C2 symmetry in spin excitations above TN is produced by vestigial three-state Potts nematic order rather than by residual short-range magnetic correlations or by strain-induced shifts in exchange parameters that have nothing to do with nematicity.
What would settle it
A measurement showing that spin excitations recover full C3 symmetry above TN when uniaxial strain is removed, or when short-range correlations are eliminated by temperature or doping while strain is still applied.
Figures
read the original abstract
In two-dimensional (2D) nearly square-lattice quantum materials, electron correlations can induce an electronic nematic phase with twofold rotational ($C_2$) symmetry that profoundly impacts their properties. For 2D materials with threefold rotational ($C_3$) symmetry, such as the honeycomb lattice, a vestigial three-state Potts nematic order has been observed in the van der Waals antiferromagnet (AFM) FePSe$_3$ via optical and thermodynamic methods under uniaxial strain. Here, we use neutron scattering to study the magnetic order and spin excitations of FePSe$_3$ under uniaxial strain. In the AFM ordered state, we find that $\sim$0.6% tensile strain significantly suppresses one zigzag domain and promotes the other two, lowering the AFM order and spin waves to $C_2$ symmetry. The broken $C_3$ symmetry in spin excitations persists slightly above $T_{\rm{N}}\approx 108.6$ K, where the zigzag AFM order is absent. Our results thus provide direct evidence of magnetoelastic coupling and suggest that the three-state Potts nematicity in paramagnetic spin excitations arises from the vestigial order associated with the low-temperature zigzag AFM order.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript reports neutron scattering measurements on the van der Waals antiferromagnet FePSe₃ under uniaxial strain. It finds that ~0.6% tensile strain suppresses one zigzag AFM domain while promoting the other two, reducing both the magnetic order and spin-wave excitations to C₂ symmetry. The central claim is that this broken C₃ symmetry in the spin excitations persists slightly above T_N ≈ 108.6 K (where long-range zigzag order vanishes), providing evidence of magnetoelastic coupling and indicating that the three-state Potts nematicity in the paramagnetic phase is a vestigial order tied to the low-temperature AFM state.
Significance. If the interpretation is robust, the work supplies momentum-resolved neutron data that directly links strain-tuned domain populations to symmetry breaking in spin excitations, extending prior optical and thermodynamic observations of vestigial Potts nematicity. The experimental approach of applying uniaxial strain while tracking both ordered and paramagnetic regimes is a clear strength and offers a concrete test of magnetoelastic effects in a C₃-symmetric honeycomb lattice material. The absence of quantitative controls, however, leaves the distinction between true vestigial order and alternative strain-induced short-range correlations unresolved.
major comments (2)
- [Abstract] Abstract (final sentence) and discussion of paramagnetic regime: The claim that the observed C₂ anisotropy above T_N constitutes direct evidence of vestigial three-state Potts nematic order is not quantitatively supported. No temperature scaling of the anisotropy relative to the magnetic correlation length, nor any comparison to nematic susceptibility, is presented to rule out strain-modified exchange parameters or short-range zigzag fluctuations that themselves break C₃ symmetry in the paramagnetic state.
- [Results (paramagnetic phase)] Results on spin excitations above T_N: The intensity maps and dispersion relations showing persistent C₂ symmetry lack reported error bars, background-subtraction procedures, and control data taken without applied strain. These omissions prevent a clear assessment of whether the high-temperature C₂ signal is intrinsic or arises from residual short-range correlations or experimental artifacts.
minor comments (2)
- [Methods/Figure captions] The strain value (~0.6%) and its orientation relative to the honeycomb lattice should be stated more explicitly in the methods or figure captions to allow direct comparison with theoretical models of magnetoelastic coupling.
- [Experimental details] A brief statement on the instrumental resolution and any corrections applied to the spin-wave data would improve clarity without altering the central claims.
Simulated Author's Rebuttal
We thank the referee for the thoughtful and constructive review of our manuscript. The comments help clarify the presentation of our evidence for vestigial three-state Potts nematicity. Below we respond point by point to the major comments. We have revised the manuscript to address the concerns where possible while maintaining the integrity of our experimental claims.
read point-by-point responses
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Referee: [Abstract] Abstract (final sentence) and discussion of paramagnetic regime: The claim that the observed C₂ anisotropy above T_N constitutes direct evidence of vestigial three-state Potts nematic order is not quantitatively supported. No temperature scaling of the anisotropy relative to the magnetic correlation length, nor any comparison to nematic susceptibility, is presented to rule out strain-modified exchange parameters or short-range zigzag fluctuations that themselves break C₃ symmetry in the paramagnetic state.
Authors: We agree that a quantitative scaling analysis would further strengthen the interpretation. However, the selective suppression of one zigzag domain under strain, which directly imprints C₂ symmetry onto the spin excitations both below and above T_N, is difficult to reconcile with uniform strain-modified exchange parameters (which would not preferentially select domains). Short-range zigzag fluctuations in the paramagnetic state would also be expected to average over all three domains in the absence of strain, yet our data show the anisotropy only appears under the same strain conditions that select domains in the ordered phase. We have added a dedicated paragraph in the revised discussion section that qualitatively compares the temperature dependence of the anisotropy to the magnetic correlation length extracted from the quasielastic scattering and explicitly contrasts the observations with strain-renormalized exchange scenarios. A full quantitative nematic susceptibility analysis lies beyond the present dataset but is noted as a direction for future work. revision: partial
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Referee: [Results (paramagnetic phase)] Results on spin excitations above T_N: The intensity maps and dispersion relations showing persistent C₂ symmetry lack reported error bars, background-subtraction procedures, and control data taken without applied strain. These omissions prevent a clear assessment of whether the high-temperature C₂ signal is intrinsic or arises from residual short-range correlations or experimental artifacts.
Authors: We thank the referee for pointing out these presentational gaps. In the revised manuscript we have added statistical error bars to all intensity maps and dispersion cuts in the paramagnetic regime. The background-subtraction procedure (using empty-can measurements scaled to the sample volume and temperature) is now described in the Methods section with explicit reference to the supplementary figures. Control data without applied strain are shown in Supplementary Figure S3, demonstrating that the spin excitations remain C₃-symmetric in the unstrained paramagnetic phase; the C₂ anisotropy appears only when uniaxial strain is applied. These additions allow the reader to assess that the high-temperature signal is not an artifact. revision: yes
Circularity Check
No circularity: experimental symmetry observations are direct measurements, not derived from fitted inputs or self-citations
full rationale
The manuscript presents neutron scattering intensity maps, dispersion relations, and domain populations in FePSe3 under applied strain. These are reported as raw experimental results (e.g., suppression of one zigzag domain and persistence of C2 symmetry slightly above TN). No equations, ansatze, or predictions are introduced that reduce by construction to a fitted parameter, a self-citation chain, or a renamed empirical pattern. The interpretation linking the data to vestigial three-state Potts nematicity is offered as a suggestion supported by prior optical/thermodynamic work, but the central claims remain independent measurements that can be checked against the reported spectra and temperature dependence without circular reduction.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Neutron scattering intensity maps spin-wave dispersion and domain populations in antiferromagnets
- domain assumption Uniaxial strain couples to magnetic anisotropy via magnetoelastic interaction
Lean theorems connected to this paper
-
IndisputableMonolith/Foundation/AlexanderDuality.leanalexander_duality_circle_linking unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
The broken C3 symmetry in spin excitations persists slightly above TN≈108.6 K, where the zigzag AFM order is absent, providing direct evidence of magnetoelastic coupling and suggesting that the three-state Potts nematicity arises from the vestigial order associated with the low-temperature zigzag AFM order.
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]
A. J. Beekman, L. Rademaker, and J. van Wezel, SciPost Phys. Lect. Notes , 11 (2019)
work page 2019
-
[2]
N. W. Ashcroft and N. D. Mermin, Solid State Physics (Holt-Saunders, New York, 1976)
work page 1976
-
[3]
P.-G. De Gennes and J. Prost, The physics of liquid crys- tals, 83 (Oxford University Press, 1993)
work page 1993
-
[4]
S. A. Kivelson, E. Fradkin, and V. J. Emery, Nature 393, 550 (1998)
work page 1998
-
[5]
E. Fradkin, S. A. Kivelson, M. J. Lawler, J. P. Eisenstein, and A. P. Mackenzie, Annu. Rev. Condens. Matter Phys. 1, 153 (2010)
work page 2010
-
[6]
R. M. Fernandes, P. P. Orth, and J. Schmalian, Annual Review of Condensed Matter Physics 10, 133 (2019)
work page 2019
-
[7]
L. Nie, G. Tarjus, and S. A. Kivelson, Proceedings of 6 the National Academy of Sciences 111, 7980 (2014)
work page 2014
- [8]
-
[9]
A. E. B¨ ohmer, J.-H. Chu, S. Lederer, and M. Yi, Nature Physics 18, 1412 (2022)
work page 2022
- [10]
-
[11]
J.-H. Chu, J. G. Analytis, K. D. Greve, P. L. McMahon, Z. Islam, Y. Yamamoto, and I. R. Fisher, Science 329, 824 (2010)
work page 2010
-
[12]
In two-dimensional systems of interest, the C6 group can be generated by the C3 and C2 subgroups. Since the nematic state retains C2 symmetry, the distinctions be- tween C3 and C6 symmetries become irrelevant, render- ing them effectively equivalent in this context
-
[13]
R. M. Fernandes and J. W. F. Venderbos, Science Ad- vances 6, eaba8834 (2020)
work page 2020
-
[14]
A. R. Chakraborty and R. M. Fernandes, Phys. Rev. B 107, 195136 (2023)
work page 2023
-
[15]
Y. Xie, A. Hardy, and A. Paramekanti, Phys. Rev. B 110, 165158 (2024)
work page 2024
- [16]
- [17]
-
[18]
E. Kirstein, P. Park, W. Cho, C. D. Batista, J.-G. Park, and S. A. Crooker, arXiv preprint arXiv:2507.08148 (2025)
-
[19]
L. Nie, K. Sun, W. Ma, D. Song, L. Zheng, Z. Liang, P. Wu, F. Yu, J. Li, M. Shan, D. Zhao, S. Li, B. Kang, Z. Wu, Y. Zhou, K. Liu, Z. Xiang, J. Ying, Z. Wang, T. Wu, and X. Chen, Nature 604, 59 (2022)
work page 2022
-
[20]
Y. Xu, Z. Ni, Y. Liu, B. R. Ortiz, Q. Deng, S. D. Wilson, B. Yan, L. Balents, and L. Wu, Nature physics 18, 1470 (2022)
work page 2022
- [21]
-
[22]
C. Farhang, W. R. Meier, W. Lu, J. Li, Y. Wu, S. Mozaf- fari, R. P. Madhogaria, Y. Zhang, D. Mandrus, and J. Xia, Nature Communications 16, 7867 (2025)
work page 2025
-
[23]
K. Hwangbo, E. Rosenberg, J. Cenker, Q. Jiang, H. Wen, D. Xiao, J.-H. Chu, and X. Xu, Nature Physics 20, 1888 (2024)
work page 2024
- [24]
-
[25]
Q. Tan, C. A. Occhialini, H. Gao, J. Li, H. Kitadai, R. Comin, and X. Ling, Nano Letters 24, 7166 (2024)
work page 2024
- [26]
-
[27]
Q. H. Wang, A. Bedoya-Pinto, M. Blei, A. H. Dismukes, A. Hamo, S. Jenkins, M. Koperski, Y. Liu, Q.-C. Sun, E. J. Telford, H. H. Kim, M. Augustin, U. Vool, J.- X. Yin, L. H. Li, A. Falin, C. R. Dean, F. Casanova, R. F. L. Evans, M. Chshiev, A. Mishchenko, C. Petrovic, R. He, L. Zhao, A. W. Tsen, B. D. Gerardot, M. Brotons- Gisbert, Z. Guguchia, X. Roy, S. ...
work page 2022
-
[28]
J. Cui, E. V. Bostr¨ om, M. Ozerov, F. Wu, Q. Jiang, J.- H. Chu, C. Li, F. Liu, X. Xu, A. Rubio, A. Rubio, and Q. Zhang, Nature Communications 14, 3396 (2023)
work page 2023
-
[29]
Haglund, Thermal conductivity of MXY 3 magnetic layered trichalcogenides, Ph.D
A. Haglund, Thermal conductivity of MXY 3 magnetic layered trichalcogenides, Ph.D. thesis, University of Ten- nessee, Knoxville, TN (2019), ph.D. dissertation
work page 2019
-
[30]
L. Chen, X. Teng, D. Hu, F. Ye, G. E. Granroth, M. Yi, J.-H. Chung, R. J. Birgeneau, and P. Dai, npj Quantum Materials 9, 40 (2024)
work page 2024
-
[31]
A. Wiedenmann, J. Rossat-Mignod, A. Louisy, R. Brec, and J. Rouxel, Solid State Communications 40, 1067 (1981)
work page 1981
-
[32]
A. Bhutani, J. L. Zuo, R. D. McAuliffe, C. R. dela Cruz, and D. P. Shoemaker, Phys. Rev. Mater. 4, 034411 (2020)
work page 2020
-
[33]
Z. Mo, C. Li, W. Zhang, C. Liu, Y. Sun, R. Liu, and X. Lu, Chinese Physics Letters 41, 107102 (2024)
work page 2024
-
[34]
S. Toth and B. Lake, Journal of Physics: Condensed Mat- ter 27, 166002 (2015)
work page 2015
-
[35]
X. Lu, J. T. Park, R. Zhang, H. Luo, A. H. Nevidomskyy, Q. Si, and P. Dai, Science 345, 657 (2014)
work page 2014
-
[36]
M. G. Kim, R. M. Fernandes, A. Kreyssig, J. W. Kim, A. Thaler, S. L. Bud’ko, P. C. Canfield, R. J. McQueeney, J. Schmalian, and A. I. Goldman, Phys. Rev. B 83, 134522 (2011)
work page 2011
- [37]
-
[38]
P. Liu, M. L. Klemm, L. Tian, X. Lu, Y. Song, D. W. Tam, K. Schmalzl, J. Park, Y. Li, G. Tan, Y. Su, F. Bour- darot, Y. Zhao, J. W. Lynn, R. J. Birgeneau, and P. Dai, Nature Communications 11, 5728 (2020)
work page 2020
-
[39]
D. W. Tam, W. Wang, L. Zhang, Y. Song, R. Zhang, S. V. Carr, H. C. Walker, T. G. Perring, D. T. Adroja, and P. Dai, Phys. Rev. B 99, 134519 (2019)
work page 2019
-
[40]
R. Liu, M. B. Stone, S. Gao, M. Nakamura, K. Ka- mazawa, A. Krajewska, H. C. Walker, P. Cheng, R. Yu, Q. Si, P. Dai, and X. Lu, Nature Communications 16, 5212 (2025)
work page 2025
-
[41]
See Supplemental Material [url] for additional data and analyses
- [42]
-
[43]
X. Lu, W. Zhang, Y. Tseng, R. Liu, Z. Tao, E. Paris, P. Liu, T. Chen, V. N. Strocov, Y. Song, R. Yu, Q. Si, P. Dai, and T. Schmitt, Nature Physics 18, 806 (2022)
work page 2022
- [44]
- [45]
-
[46]
O. Arnold et al. , Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 764, 156 (2014)
work page 2014
- [47]
-
[48]
G. Xu, Z. Xu, and J. M. Tranquada, Review of Scientific Instruments 84, 083906 (2013). 1 Supplemental Material for “Signatures of three-state Potts nematicity in spin excitations of the van der Waals antiferromagnet FePSe 3” I. FEPSE 3 SINGLE CR YST AL GROWTH AND CHARACTERIZA TION High-quality FePSe3 single crystals were synthesized using a chemical vapor...
work page 2013
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