REVIEW 3 major objections 4 minor 37 references
Polarization switching in sliding ferroelectrics: the roles of fluctuation and domain wall
T0 review · 3 major / 4 minor · reviewed 2026-08-15 · deepseek-v4-flash
Pith's one-line read Sliding ferroelectricity in bilayer h-BN switches by avalanche rather than by climbing a fixed intrinsic energy barrier, because off-diagonal Born effective charges couple a vertical electric field to horizontal ionic motion.
desk verdict A solid ab initio case that off-diagonal Born effective charges and C3 symmetry make h-BN sliding switching avalanche-like, with quantitative coercive fields that are static estimates rather than dynamical predictions. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central object is the Born effective charge tensor $Z^*_{\kappa,ij}$, defined as the change of polarization of ion $\kappa$ along direction $i$ due to a unit displacement along $j$ (equivalently the force on the ion from an electric field). In h-BN, its off-diagonal element $Z^*_{xz}$ vanishes in the AB/BA ferroelectric states by C3 symmetry, becomes finite and peaks sharply at the P=0 saddle-point state, and its layer sum governs the perpendicular field-to-sliding coupling. The paper uses this tensor together with the intrinsic resistance force $f^r$ from the energy barrier to estimate the required critical field $E^r_z = f^r/Z^*_{xz}$ along the switching path. That ratio is the mechanism that converts a symmetric barrier into an avalanche: the denominator grows at intermediate sliding, so the field needed to continue sliding falls even as the resistance force rises.
What would settle it
Measure polarization reversal in an ultraclean, strain-free, atomically flat h-BN bilayer at low temperature under a perfectly homogeneous vertical electric field; the paper predicts zero or near-zero probability of switching unless a symmetry-breaking perturbation nucleates sliding, so observing low-field uniform switching would falsify the avalanche picture.
Extended reading notes
Core claim
For bilayer h-BN, the paper's key finding is that the off-diagonal Born effective charge tensor element $Z^*_{xz}$, which is exactly zero in the high-symmetry AB/BA ferroelectric states due to in-plane C3 symmetry, becomes nonzero as soon as the layers slide. Because the electrostatic force on an ion is $f_i = E_j Z^*_{ij}$, this nonzero $Z^*_{xz}$ provides the perpendicular coupling that lets an out-of-plane field drive in-plane motion. The resistance force from the energy barrier rises then falls, but the required critical field $E^r_z = f^r/Z^*_{xz}$ monotonically decreases with sliding, starting from an arbitrarily high value at the symmetric state and reaching a minimum near P=0, then rising as $Z^*_{xz}$ vanishes again. This avalanche-like behavior means the measured coercive field is set by the initial symmetry-breaking perturbation, not by an intrinsic maximum. The authors also show that the large $Z^*_{xz}$ near the P=0 intermediate state makes the center of a domain wall move faster than its flanks, producing a wriggling motion that may explain the high switching speeds reported experimentally.
Load-bearing premise
The load-bearing premise is that the quasistatic force-balance estimate $E^r_z = f^r/Z^*_{xz}$, evaluated at frozen intermediate configurations starting from an arbitrary tiny sliding of 0.045 Å, represents the real switching trajectory; if inertia, dissipation, or field-dependent deformation changes that path, the monotonic decrease and coercive values would not hold.
Editorial extensions
If this is right
- The coercive field of sliding ferroelectrics is not a material constant; it can be engineered by strain, wrinkles, interlayer spacing, temperature, and domain-wall density.
- Any C3-breaking perturbation, including thermal fluctuations, twist, edges, or defects, can nucleate switching, so nominally identical samples may show very different switching fields depending on preparation.
- The avalanche mechanism should appear in other C3-symmetric sliding ferroelectrics, including 3R-MoS2 bilayers and MoS2/WS2 heterobilayers, not just h-BN.
- The leading role of the domain-wall center means switching speed is governed by the large off-diagonal Born effective charge near P=0, which could account for the observed ultrafast polarization reversal.
Reading between the lines
- If the avalanche picture is right, measurements of switching statistics on nominally identical h-BN devices should show a distribution of coercive fields, with the tail controlled by the largest thermal fluctuation or local wrinkle; this is a testable corollary the paper does not pursue.
- The C3 symmetry-selection rule suggests that a perfectly homogeneous vertical field cannot switch a defect-free, unstrained, zero-temperature h-BN bilayer at any field strength, so the paper's switching mechanism implicitly relies on a fluctuating or inhomogeneous environment.
- One could extend the calculation to the dynamics of a single domain wall under an electric-field pulse to obtain a predicted wall velocity, connecting the quasistatic estimates to the experimentally measured switching times.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This Letter uses DFPT and AIMD to study polarization switching in bilayer h-BN as a model sliding ferroelectric. The authors compute off-diagonal Born effective charges Z*_xz along the AB→SP→BA sliding path (Path II) and show that an out-of-plane electric field exerts an in-plane force proportional to Z*_xz. They find that the quasistatic balance field E^r_z = f^r/Z*_xz decreases monotonically with sliding, in contrast to conventional ferroelectrics such as BaTiO3 where it peaks mid-path. They further analyze how a field-induced layer wrinkle, the interlayer gap, temperature, and the presence of domain walls modify Z*_xz, f^r, and hence E^r_z, concluding that any perturbation breaking the in-plane C3 symmetry assists an avalanche-like switching process. The paper reports AIMD showing polarization switching at 250 K under E_z = 0.2 V/Å and static estimates predicting a much larger zero-temperature coercive field. Domain-wall calculations show enhanced off-diagonal Z* near the wall center, which the authors propose leads to a wriggling motion of domain walls.
Significance. If the avalanche-like switching picture is correct, it would explain why experimental coercive fields in sliding ferroelectrics are far below the naive barrier-derived estimates and why switching can be ultrafast. The identification of off-diagonal Born effective charges as the coupling mechanism is a valuable step and is supported by independent DFPT calculations. The paper's strengths include a clean benchmark against BaTiO3, explicit consideration of wrinkle and gap dependences, AIMD support for room-temperature switching at low fields, and an open disclosure of two overlapping preprints. However, the dynamical conclusions (avalanche and domain-wall wriggling) are inferred from static calculations and require either additional simulation or more careful wording.
major comments (3)
- [Eq. (2) and Fig. 1(f)] The coercive field curve E^r_z = f^r/Z*_xz is a quasistatic force balance evaluated at zero-field relaxed geometries along Path II, starting from an arbitrarily chosen initial sliding s = 0.045 Å. This calculation demonstrates that the static balance field decreases with sliding, but it does not by itself demonstrate avalanche-like switching dynamics, which requires a time-dependent or finite-field instability. The paper contains no simulation of the switching trajectory under a sustained field; the AIMD in Fig. 3(b) shows switching at 250 K with E_z = 0.2 V/Å but is not analyzed in terms of the force-balance curve. Please either add a self-consistent finite-field calculation or a direct time-dependent simulation (e.g., AIMD with the field on from the start) to support the avalanche claim, or revise the wording throughout (abstract, Fig. 1(f)) to 'the static critical field decreases monotonically with sliding' rather than 'avalanche-like switching dynamics.'
- [Fig. 2(c)-(d)] The wrinkle reduction of E^r_z is not self-consistent. The wrinkle amplitude \bar h is the equilibrium response to E_z (Fig. 2c, linear growth), but the reported E^r_z = 0.61 V/Å at \bar h = 0.01 Å is obtained by inserting the \bar h = 0.01 Å structure into the zero-field formula E^r_z = f^r/Z*_xz with s = 0.045 Å fixed. The paper does not verify that E_z = 0.61 V/Å actually produces \bar h = 0.01 Å in the staggered geometry, nor that the finite field leaves Z*_xz and f^r unchanged. If the field needed for \bar h = 0.01 Å differs from 0.61 V/Å, the claimed reduction to about one quarter is not a fixed point of the coupled problem. Please perform a self-consistent calculation (relax under a fixed E_z and recompute Z* and f^r at that geometry) or explicitly state the E_z value corresponding to \bar h = 0.01 Å and check the consistency.
- [Paragraph beginning 'Finally, it is worth to investigate...' and Fig. 4] The 'wriggling motion' of domain walls is inferred from the static spatial profile of Z*_xz and Z*_yz in a relaxed domain-wall supercell. No dynamical simulation of the domain wall under E_z is reported, and the text itself states this 'warranting further investigation.' As written, the abstract and concluding sentence present the wriggling as a result ('results in a wriggling motion of domain walls'), which overstates the evidence. Please either add a minimal time-dependent simulation (e.g., MD of the DW under a field) or label the wriggling explicitly as a qualitative prediction, and adjust the abstract accordingly.
minor comments (4)
- [Reference [28]] The Supplemental Material reference [28] contains a corrupted citation string 'including Refs. [13, 24? ? ? ? ? ? ? ? ?]'; this must be repaired before publication.
- [Fig. 1(f) and text near 'Beginning from a staggered stacking mode'] The choice of initial sliding s = 0.045 Å is arbitrary; please justify it from the thermal fluctuation amplitude at 250 K or provide a short sensitivity study over s to show that the monotonic decrease of E^r_z is robust.
- [Fig. 3(c)] Fig. 3(c) reports a temperature-dependent coercive field estimated from AIMD, but the main text does not describe the AIMD protocol (e.g., how E_z is ramped, what polarization threshold defines switching). Please specify the protocol in the main text or refer the reader to a detailed SM section.
- [Fig. 2(d) and text] The quantity \bar h is used in Fig. 2(d) but defined only in the caption; please define it in the body text before the discussion of the wrinkle effect.
Circularity Check
No significant circularity: the switching mechanism follows from independently computed Born effective charges and energy barriers, not from fitted or self-cited inputs.
full rationale
I find no circular step. The central relation E^r_z = f^r / Z*_xz is an algebraic definition of the field needed to balance the computed intrinsic resistance, but the physical content is the ab initio evaluation of Z*_xz and f^r along the switching path. The off-diagonal Born effective charges are obtained by DFPT at frozen intermediate geometries, not imposed to produce the conclusion. The monotonically decreasing E^r_z profile and the 'avalanche-like' interpretation follow from those computed numbers. The initial sliding s = 0.045 Å and the wrinkle amplitude bar h = 0.01 Å are hand-set structural inputs that affect quantitative values, but they are not fitted to the experimental coercive field; the comparison with the measured ~0.03 V/Å is presented as a physical discrepancy motivating wrinkle, gap, and temperature effects rather than as a fitting target. The d- and bar-h-dependent scans and the AIMD simulations are additional first-principles calculations. The two recent preprints acknowledged in the Note are not used to justify the present derivation, and the domain-wall 'wriggling' is explicitly left as 'warranting further investigation'. The self-citations are background or previously established structural statements and are not load-bearing. The static force-balance assumption and the non-self-consistent treatment of field-induced wrinkling are modeling limitations, but they are not circular reductions of the result to its inputs.
Assumptions & free parameters
free parameters (3)
- initial sliding displacement s =
0.045 Å
- wrinkle amplitude hbar =
0.01 Å
- interlayer gap d =
3.62 Å
assumptions (4)
- domain assumption The force on an ion in a periodic insulator under an electric field is f^E_κ,i = Σ_j E_j Z*_κ,ij (Eq. 2), with Z* from DFPT.
- domain assumption Switching occurs quasistatically when the electrostatic force overcomes the intrinsic resistance f^r = -∂H/∂u; dynamics are not integrated for the single-domain coercive field.
- standard math The vertical electric field preserves the in-plane C3 symmetry, so Z*_xz=0 exactly at the AB and BA stacks.
- domain assumption DFT/DFPT/AIMD with the chosen functional, vdW correction, and supercell sizes describe h-BN polarization and switching.
Cite this review
Pith. "Pith review of Polarization switching in sliding ferroelectrics: the roles of fluctuation and domain wall." pith.science (2026). https://pith.science/paper/LBK4ZZGJ
@misc{pith2026250509084,
author = {Pith},
title = {Pith review of: Polarization switching in sliding ferroelectrics: the roles of fluctuation and domain wall},
year = {2026},
howpublished = {\url{https://pith.science/paper/LBK4ZZGJ}},
note = {Machine review of arXiv:2505.09084}
}
abstract
Sliding ferroelectricity is highly attractive for its low energy barriers and fatigue resistance. As the origin of these exotic properties, its unconventional switching dynamics remains poorly understood: how an electric field drives a perpendicular sliding? Taking $h$-BN bilayer as a model system, its switching dynamics is studied using \textit{ab initio} calculations. The off-diagonal Born effective charge leads to the perpendicular relationship between the electric field and ionic movements. Interestingly, the rules of intrinsic coercive field are distinct between $h$-BN bilayer and conventional ferroelectrics. For $h$-BN bilayer, any perturbation breaking the in-plane symmetry plays a key role to assist the avalanche-like switching dynamics. Moreover, the exotic large off-diagonal Born effective charge near the $P=0$ intermediate state results in a wriggling motion of domain walls in $h$-BN bilayer. Our results reveal the key factors in the ferroelectric switching of sliding ferroelectrics at room temperature.
Figures
Reference graph
Works this paper leans on
-
[1]
J. F. Scott, Applications of modern ferroelectrics, Science 315, 954 (2007)
2007
-
[2]
K. Rabe, C. H. Ahn, and J.-M. Triscone, eds.,Physics of Ferroelectrics: A Modern Perspective(Springer, 2007)
work page 2007
-
[3]
S. Li, F. Wang, Y. Wang, J. Yang, X. Wang, X. Zhan, J. He, and Z. Wang, Van der waals ferroelectrics: Theo- ries, materials, and device applications, Adv. Mater.36, 2301472 (2024)
work page 2024
-
[4]
C. Wang, L. You, D. Cobden, and J. Wang, Towards two- dimensional van der waals ferroelectrics, Nat. Mater.22, 542 (2023)
2023
-
[5]
Z. Guan, H. Hu, X. Shen, P. Xiang, N. Zhong, J. Chu, and C. Duan, Recent progress in two-dimensional fer- roelectric materials, Adv. Electron. Mater.6, 1900818 (2020)
work page 2020
-
[6]
A. Belianinov, Q. He, A. Dziaugys, P. Maksymovych, E. Eliseev, A. Borisevich, A. Morozovska, J. Banys, Y. Vysochanskii, and S. V. Kalinin, CuInP 2S6 room temperature layered ferroelectric, Nano Lett.15, 3808 (2015)
work page 2015
-
[7]
F. Liu, L. You, K. L. Seyler, X. Li, P. Yu, J. Lin, X. Wang, J. Zhou, H. Wang, H. He,et al., Room- temperature ferroelectricity in CuInP2S6 ultrathin flakes, Nat. Commun.7, 12357 (2016)
work page 2016
- [8]
Show all 37 references
-
[9]
Cui, W.-J
C. Cui, W.-J. Hu, X. Yan, C. Addiego, W. Gao, Y. Wang, Z. Wang, L. Li, Y. Cheng, P. Li, X. Zhang, H. N. Alsha- reef, T. Wu, W. Zhu, X. Pan, and L.-J. Li, Intercor- related in-plane and out-of-plane ferroelectricity in ul- trathin two-dimensional layered semiconductor In 2Se3, ...
2018
-
[10]
J. Xiao, H. Zhu, Y. Wang, W. Feng, Y. Hu, A. Dasgupta, Y. Han, Y. Wang, D. A. Muller, L. W. Martin, P. Hu, and X. Zhang, Intrinsic two-dimensional ferroelectricity with dipole locking, Phys. Rev. Lett.120, 227601 (2018)
2018
-
[11]
Y. Zhou, D. Wu, Y. Zhu, Y. Cho, Q. He, X. Yang, K. Her- rera, Z. Chu, Y. Han, M. C. Downer, H. Peng, and K. Lai, Out-of-plane piezoelectricity and ferroelectricity in lay- eredα-In 2Se3 nanoflakes, Nano Lett.17, 5508 (2017)
2017
-
[12]
J. Gou, H. Bai, X. Zhang, Y. L. Huang, S. Duan, A. Ar- iando, S. A. Yang, L. Chen, Y. Lu, and A. T. S. Wee, Two-dimensional ferroelectricity in a single-element bis- muth monolayer, Nature617, 67 (2023). 6
2023
-
[13]
Li and M
L. Li and M. Wu, Binary compound bilayer and multi- layer with vertical polarizations: Two-dimensional ferro- electrics, multiferroics, and nanogenerators, ACS Nano 11, 6382 (2017)
2017
-
[14]
M. V. Stern, Y. Waschitz, W. Cao, I. Nevo, K. Watanabe, T. Taniguchi, E. Sela, M. Urbakh, O. Hod, and M. B. Shalom, Interfacial ferroelectricity by van der waals slid- ing, Science372, 1462 (2021)
2021
-
[15]
Yasuda, X
K. Yasuda, X. Wang, K. Watanabe, T. Taniguchi, and P. Jarillo-Herrero, Stacking-engineered ferroelectricity in bilayer boron nitride, Science372, 1458 (2021)
2021
-
[16]
Wu and J
M. Wu and J. Li, Sliding ferroelectricity in 2D van der Waals materials: Related physics and future opportuni- ties, Proc. Natl. Acad. Sci. U. S. A.118, e2115703118 (2021)
2021
-
[17]
Z. Fei, W. Zhao, T. A. Palomaki, B. Sun, M. K. Miller, Z. Zhao, J. Yan, X. Xu, and D. H. Cobden, Ferroelectric switching of a two-dimensional metal, Nature560, 336 (2018)
2018
-
[18]
J. Xiao, Y. Wang, H. Wang, C. Pemmaraju, S. Wang, P. Muscher, E. J. Sie, C. M. Nyby, T. P. Devereaux, X. Qian, X. Zhang, and A. M. Lindenberg, Berry curva- ture memory through electrically driven stacking transi- tions, Nat. Phys.16, 1028 (2020)
2020
-
[19]
Y. Wan, T. Hu, X. Mao, J. Fu, K. Yuan, Y. Song, X. Gan, X. Xu, M. Xue, X. Cheng, C. Huang, J. Yang, L. Dai, H. Zeng, and E. Kan, Room-Temperature Ferroelectricity in 1T ′ -ReS2 Multilayers, Phys. Rev. Lett.128, 067601 (2022)
2022
-
[20]
R. Bian, R. He, E. Pan, Z. Li, G. Cao, P. Meng, J. Chen, Q. Liu, Z. Zhong, W. Li, and F. Liu, Developing fatigue- resistant ferroelectrics using interlayer sliding switching, Science385, 57 (2024)
2024
-
[21]
Rog´ ee, L
L. Rog´ ee, L. Wang, Y. Zhang, S. Cai, P. Wang, M. Chhowalla, W. Ji, and S. P. Lau, Ferroelectricity in untwisted heterobilayers of transition metal dichalco- genides, Science376, 973 (2022)
2022
-
[22]
L.-P. Miao, N. Ding, N. Wang, C. Shi, H.-Y. Ye, L. Li, Y.-F. Yao, S. Dong, and Y. Zhang, Direct observation of geometric and sliding ferroelectricity in an amphidy- namic crystal, Nat. Mater.21, 1158 (2022)
2022
-
[23]
Yang and S
Q. Yang and S. Meng, Light-induced complete reversal of ferroelectric polarization in sliding ferroelectrics, Phys. Rev. Lett.133, 136902 (2024)
2024
-
[24]
J. Wang, X. Li, X. Ma, L. Chen, J.-M. Liu, C.-G. Duan, J. ´I˜ niguez Gonz´ alez, D. Wu, and Y. Yang, Ultrafast switching of sliding polarization and dynamical magnetic field in van der Waals bilayers induced by light, Phys. Rev. Lett.133, 126801 (2024)
2024
-
[25]
Liang, D
J. Liang, D. Yang, J. Wu, Y. Xiao, K. Watanabe, T. Taniguchi, J. I. Dadap, and Z. Ye, Resolving polar- ization switching pathways of sliding ferroelectricity in trilayer 3R-MoS2, Nat. Nanotechnol. (2025)
2025
-
[26]
Yasuda, E
K. Yasuda, E. Zalys-Geller, X. Wang, D. Bennett, S. S. Cheema, K. Watanabe, T. Taniguchi, E. Kaxi- ras, P. Jarillo-Herrero, and R. Ashoori, Ultrafast high- endurance memory based on sliding ferroelectrics, Sci- ence385, 53 (2024)
2024
-
[27]
R. He, B. Zhang, H. Wang, L. Li, P. Tang, G. Bauer, and Z. Zhong, Ultrafast switching dynamics of the ferro- electric order in stacking-engineered ferroelectrics, Acta Mater.262, 119416 (2024)
2024
-
[28]
[13, 24? ? ? ? ? ? ? ? ? ]
See Supplemental Material [url] for methods, complete Born effective charge tensor of barium and oxygen of BaTiO3; energy barrier of the switching path of BaTiO3; lattice constant and polarization ofh-BN bilayer with dif- ferent exchange-correlation functionals and vdW correc-...
-
[29]
Constantinescu, A
G. Constantinescu, A. Kuc, and T. Heine, Stacking in bulk and bilayer hexagonal boron nitride, Phys. Rev. Lett.111, 036104 (2013)
2013
-
[30]
J. H. Warner, M. H. R¨ ummeli, A. Bachmatiuk, and B. B¨ uchner, Atomic resolution imaging and topography of boron nitride sheets produced by chemical exfoliation, ACS Nano4, 1299 (2010)
2010
-
[31]
Gonze and C
X. Gonze and C. Lee, Dynamical matrices, born effective charges, dielectric permittivity tensors, and interatomic force constants from density-functional perturbation the- ory, Phys. Rev. B55, 10355 (1997)
1997
-
[32]
Ghosez and X
P. Ghosez and X. Gonze, Band-by-band decompositions of the born effective charges, J. Phys.: Condens. Matter 12, 9179 (2000)
2000
-
[33]
Ghosez, J.-P
P. Ghosez, J.-P. Michenaud, and X. Gonze, Dynamical atomic charges: the case of ABO 3 compounds, Phys. Rev. B58, 6224 (1998)
1998
-
[34]
Wang and S
Z. Wang and S. Dong, Large in-plane negative piezo- electricity and giant nonlinear optical susceptibility in elementary ferroelectric monolayers, Phys. Rev. B108, 235423 (2023)
2023
-
[35]
N. Ding, J. Chen, C. Gui, H. You, X. Yao, and S. Dong, Phase competition and negative piezoelectricity in interlayer-sliding ferroelectric ZrI 2, Phys. Rev. Mater. 5, 084405 (2021)
2021
-
[36]
C. Ke, F. Liu, and S. Liu, Superlubric motion of wave-like domain walls in sliding ferroelectrics (2025), arXiv:2502.01007
2025 arXiv
-
[37]
Y. Shi, Y. Gao, R. He, H. Wang, B. Zhang, and Z. Zhong, Undamped soliton-like domain wall motion in sliding fer- roelectrics (2025), arXiv:2502.02137
2025 arXiv
Reviewed August 15, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.