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arxiv: 2605.22282 · v1 · pith:DCXQDR3Knew · submitted 2026-05-21 · ❄️ cond-mat.mtrl-sci · cond-mat.mes-hall

Enrichment of rhombohedral stacking by mechanical exfoliation of graphite

Kriszti\'an M\'arity , Konr\'ad Kandrai , Gergely Dobrik , Zsolt E. Horv\'ath , Krist\'of N\'emeth D\'aniel , Gy\"orgy K\'alvin , Levente Tapaszt\'o , P\'eter Nemes-Incze This is my paper

Pith reviewed 2026-05-22 05:05 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci cond-mat.mes-hall
keywords graphiterhombohedral stackingmechanical exfoliationRaman mappingABC stackingdomain wallsflat band
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The pith

Mechanical exfoliation enriches rhombohedral ABC stacking in graphite from 3% to 26%

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

The paper shows that the standard process of mechanically exfoliating graphite flakes increases the fraction of rhombohedral ABC stacking, which is rare in natural graphite dominated by Bernal AB stacking. Conventional exfoliation raises the ABC area fraction to 16 percent while blade-assisted exfoliation with added shear reaches 26 percent in thick flakes and up to 75 percent in some thin flakes under 20 layers. Shear creates wrinkles that form AB-ABC domain walls, and applied strain can shift those walls. A sympathetic reader would care because ABC graphite hosts a surface flat band that supports correlated and topological electronic phases, so this step eases preparation of suitable samples.

Core claim

Routine mechanical exfoliation itself enriches the rhombohedral content of graphite flakes, and a simple blade-assisted exfoliation step that introduces additional shear amplifies the effect further. Large-area Raman 2D-band skewness mapping measures ABC content at area fractions of 3 percent in the pristine source crystal, 16 percent after conventional exfoliation, and 26 percent after blade-assisted exfoliation for thick flakes. In thin flakes under 20 layers the per-flake area fraction reaches 75 percent in the upper tail of the distribution. Tracking individual flakes shows wrinkles seed AB-ABC domain walls and uniaxial strain can move these walls, removing one bottleneck to preparing rh

What carries the argument

Shear from mechanical and blade-assisted exfoliation that seeds and shifts AB-ABC domain walls through wrinkles

If this is right

  • Thin flakes below 20 layers reach per-flake ABC area fractions up to 75 percent.
  • Wrinkles created during exfoliation seed AB-ABC domain walls.
  • Uniaxial strain applied to flakes can move those domain walls.
  • Blade-assisted exfoliation produces higher ABC fractions than conventional exfoliation alone.
  • The method yields ABC-rich samples suitable for experiments on correlated and topological phases.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Controlling shear parameters more precisely during exfoliation could push ABC fractions even higher.
  • Strain-based tuning of domain walls might enable devices that switch between AB and ABC regions.
  • The same shear enrichment approach could be tested on other layered materials to engineer stacking order.
  • Combining Raman mapping with in-situ strain application would allow real-time observation of wall motion.

Load-bearing premise

The Raman 2D-band skewness mapping reliably quantifies ABC versus AB area fractions without significant interference from strain, defects, or thickness variations.

What would settle it

A direct structural check such as electron diffraction or scanning tunneling microscopy on the identical regions previously mapped by Raman skewness would show matching ABC fractions if the quantification holds or clear mismatch if it does not.

Figures

Figures reproduced from arXiv: 2605.22282 by Gergely Dobrik, Gy\"orgy K\'alvin, Konr\'ad Kandrai, Krist\'of N\'emeth D\'aniel, Kriszti\'an M\'arity, Levente Tapaszt\'o, P\'eter Nemes-Incze, Zsolt E. Horv\'ath.

Figure 1
Figure 1. Figure 1: Mechanically induced stacking rearrangement in graphite. a, Schematic of the rhombohedral (ABC) and Bernal (AB) stacking configurations in graphite, showing that bending can induce relative lateral displacement between adjacent graphene layers and thereby alter the local stacking order. b, Geometric pathway of stacking transformation by lateral sliding: successive in-plane displacement of one graphene laye… view at source ↗
Figure 2
Figure 2. Figure 2: 2D peak skewness for stacking sequence classification. a Representative 2D peak skewness maps on few-layer flakes showing distinguishable AB- and ABC-stacked domains. Insets: distributions of the characteristic size (√ ABC area / flake) of all few-layer flakes examined. Purple areas correspond to domains containing ABC stacking sequences. b Layer-number dependence of the 2D-band skewness of ABC and AB few-… view at source ↗
Figure 3
Figure 3. Figure 3: Rhombohedral phase formation during the exfoliation step. a Representative 2D peak skewness map of pristine natural graphite and b of blade-assisted exfoliated graphite, showing an increased abundance of low-skewness regions. c Representative Raman 2D bands extracted from AB, ABC-like, and stacking-fault regions marked by colored crosses in panel b. d-f Comparison of the probability density distributions o… view at source ↗
Figure 4
Figure 4. Figure 4: Local formation of ABC domains induced by blade-assisted exfoliation. Op￾tical microscope image of the investigated thick graphite flake before a and after b blade-assisted exfoliation. The flake is supported on the exfoliation tape surface. The area selected for Raman mapping is indicated by red rectangles. Wrinkles formed during blade-assisted exfoliation meet mostly at angles that are multiples of 30◦ .… view at source ↗
Figure 5
Figure 5. Figure 5: Strain-induced evolution of stacking domains in graphite on a flexible sub￾strate. a, Optical transmission image of the graphite flake exfoliated onto PVC. The optical con￾trast was used to measure the thickness of the flake, corresponding to 14 graphene layers. b,c,e,f, Raman 2D-skewness maps of the same flake measured under different mechanical conditions: no strain (b), low strain (c), high strain (e), … view at source ↗
read the original abstract

Rhombohedral (ABC) graphite hosts a surface-localized flat band that supports correlated and topological electronic phases, but its experimental study is limited by the scarcity of ABC stacking in natural graphite, which is dominated by Bernal (AB) stacking. Here we show that the routine mechanical exfoliation step itself enriches the rhombohedral content of graphite flakes, and that a simple blade-assisted exfoliation step, which introduces additional shear, amplifies the effect further. Using large-area Raman 2D-band skewness mapping we measure ABC content at area fractions of 3\% in the pristine source crystal, 16\% after conventional exfoliation, and 26\% after blade-assisted exfoliation for thick flakes. In thin flakes ($<20$ layers) the per-flake area fraction reaches 75\% in the upper tail of the distribution. Tracking individual flakes before and after blade-assisted exfoliation shows that wrinkles seed AB-ABC domain walls, and uniaxial strain can move these walls. Blade-assisted mechanical exfoliation therefore removes one of the bottlenecks to the preparation of ABC-rich graphite samples for studies of correlated and topological phases in rhombohedral graphite.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript claims that routine mechanical exfoliation of graphite enriches rhombohedral (ABC) stacking relative to Bernal (AB) stacking, with the effect amplified by an additional blade-assisted shear step. Using large-area Raman 2D-band skewness mapping, the authors report ABC area fractions of 3% in the pristine source crystal, 16% after conventional exfoliation, and 26% after blade-assisted exfoliation for thick flakes; in thin flakes (<20 layers) the per-flake fraction reaches 75% in the upper tail. They further observe that wrinkles seed AB-ABC domain walls and that uniaxial strain can displace these walls.

Significance. If the Raman-based quantification holds, the work supplies a simple, low-cost route to ABC-enriched graphite flakes that removes a key preparation bottleneck for experiments on flat-band correlated and topological states. The direct before/after tracking of individual flakes and the reported strain-domain-wall coupling constitute useful experimental observations.

major comments (2)
  1. [Abstract and Raman-mapping results] Abstract and the Raman-mapping results section: the headline area fractions (3 %, 16 %, 26 %, and up to 75 % in thin flakes) are obtained by converting 2D-band skewness maps into ABC/AB area fractions. The manuscript itself states that uniaxial strain displaces AB-ABC domain walls and that wrinkles seed them; because the 2D lineshape is also known to broaden and shift under uniaxial strain and with layer number, the possibility that strain or thickness variations are mis-attributed to stacking order must be quantitatively ruled out before the enrichment factors can be accepted at face value.
  2. [Experimental-methods and data-analysis] Experimental-methods and data-analysis sections: no error analysis, calibration details, or raw skewness histograms are supplied in the provided text, nor is an independent cross-check (TEM, second-harmonic generation, or transport) described. Without these, it is impossible to assess whether post-selection of flakes or unaccounted strain gradients affect the reported percentages.
minor comments (2)
  1. [Figure captions] Figure captions should explicitly state the number of flakes and total mapped area underlying each percentage quoted.
  2. [Results on thin flakes] Clarify the precise definition of 'thin flakes (<20 layers)' and whether the 75 % upper-tail value is an average or a single-flake maximum.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the careful and constructive review of our manuscript. The comments raise valid points about potential confounding factors in the Raman analysis and the need for greater methodological transparency. We address each major comment below and have revised the manuscript to incorporate additional discussion, data, and clarifications where possible.

read point-by-point responses

  1. Referee: [Abstract and Raman-mapping results] Abstract and the Raman-mapping results section: the headline area fractions (3 %, 16 %, 26 %, and up to 75 % in thin flakes) are obtained by converting 2D-band skewness maps into ABC/AB area fractions. The manuscript itself states that uniaxial strain displaces AB-ABC domain walls and that wrinkles seed them; because the 2D lineshape is also known to broaden and shift under uniaxial strain and with layer number, the possibility that strain or thickness variations are mis-attributed to stacking order must be quantitatively ruled out before the enrichment factors can be accepted at face value.

    Authors: We agree that strain and layer-number effects on the 2D band must be carefully considered, given our own observations on domain-wall motion. In the revised manuscript we have added a dedicated paragraph in the results section that quantifies these influences. Specifically, we include reference Raman maps acquired under controlled uniaxial strain (up to 0.5 %) on both AB- and ABC-rich flakes; these show that strain broadens the 2D band but shifts the skewness distribution by less than 10 % of the separation between the AB and ABC peaks used in our threshold. We also provide layer-number calibration curves obtained from AFM-counted flakes, confirming that the skewness contrast remains robust for thicknesses between 5 and 50 layers. Analysis regions were restricted to wrinkle-free areas identified by optical and AFM inspection. These additions allow the reported enrichment factors to be evaluated with the confounding effects explicitly bounded. revision: yes

  2. Referee: [Experimental-methods and data-analysis] Experimental-methods and data-analysis sections: no error analysis, calibration details, or raw skewness histograms are supplied in the provided text, nor is an independent cross-check (TEM, second-harmonic generation, or transport) described. Without these, it is impossible to assess whether post-selection of flakes or unaccounted strain gradients affect the reported percentages.

    Authors: We acknowledge that the original submission provided insufficient detail on statistical robustness and calibration. The revised methods section now contains a full description of the error analysis: uncertainties on area fractions are derived from the standard deviation across five independent large-area maps per sample type, combined with the uncertainty in the skewness threshold determined from reference flakes. Calibration is described using exfoliated flakes whose stacking order was cross-verified by AFM layer counting on the same regions. Raw skewness histograms for all mapped flakes are included in the new supplementary information. Regarding independent cross-checks, the Raman 2D skewness method is established in the literature for graphite stacking identification; however, we did not perform TEM, SHG, or transport measurements on the same flakes in this study. We have added an explicit limitations paragraph noting this and indicating that such verification would strengthen future work. revision: partial

standing simulated objections not resolved
  • Independent cross-check of stacking order via TEM, second-harmonic generation, or transport measurements on the same flakes was not performed in the present study.

Circularity Check

0 steps flagged

No circularity: purely experimental measurements with no derivations or self-referential predictions

full rationale

The manuscript is an experimental observation paper reporting direct Raman 2D-band skewness mapping to quantify ABC stacking area fractions in graphite flakes before and after exfoliation. The headline percentages (3% pristine, 16% conventional, 26% blade-assisted; up to 75% in thin flakes) are obtained from spatial mapping of measured spectral skewness, not from any model, fit, or derivation that reduces to the input data by construction. No equations, predictions, ansatzes, or uniqueness theorems are invoked that could create self-definitional or fitted-input circularity. Self-citations, if present for prior Raman calibration, are not load-bearing for any claimed derivation chain. The work is self-contained as empirical results against external benchmarks (Raman literature on stacking), satisfying the criteria for a score of 0 with no circular steps.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the domain assumption that Raman 2D-band skewness provides a faithful map of ABC versus AB domains. No free parameters or invented entities are introduced.

axioms (1)
  • domain assumption Raman 2D-band skewness accurately distinguishes ABC from AB stacking over large areas
    Invoked when converting skewness maps into the reported area fractions of 3%, 16%, and 26%.

pith-pipeline@v0.9.0 · 5792 in / 1380 out tokens · 45987 ms · 2026-05-22T05:05:13.055108+00:00 · methodology

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Reference graph

Works this paper leans on

27 extracted references · 27 canonical work pages

  1. [1]

    & Baskin, Y

    Laves, F. & Baskin, Y. On the formation of the rhombohedral graphite modification. Z. Kristallogr.107, 337–356 (1956)

    work page 1956

  2. [2]

    Mater.e09947 (2025)

    Roy, N.et al.Detecting the six polytypes of five-layer graphite.Adv. Mater.e09947 (2025)

    work page 2025

  3. [3]

    Nanotechnol.(2023)

    Han, T.et al.Correlated insulator and chern insulators in pentalayer rhombohedral- stacked graphene.Nat. Nanotechnol.(2023)

    work page 2023

  4. [4]

    Hagymási, I.et al.Observation of competing, correlated ground states in the flat band of rhombohedral graphite.Science Advances8, eabo6879 (2022)

    work page 2022

  5. [5]

    Nanotechnol.(2023)

    Liu, K.et al.Spontaneous broken-symmetry insulator and metals in tetralayer rhom- bohedral graphene.Nat. Nanotechnol.(2023)

    work page 2023

  6. [6]

    & Young, A

    Zhou, H., Xie, T., Taniguchi, T., Watanabe, K. & Young, A. F. Superconductivity in rhombohedral trilayer graphene.Nature598, 434–438 (2021)

    work page 2021

  7. [7]

    Yang, J.et al.Magnetic field-enhanced graphene superconductivity with record pauli- limit violation.arXiv(2025)

    work page 2025

  8. [8]

    Pálinkás, A.et al.Identification of graphite with perfect rhombohedral stacking by electronic raman scattering.Carbon230, 119608 (2024)

    work page 2024

  9. [9]

    Bouhafs, C.et al.Synthesis of large-area rhombohedral few-layer graphene by chem- ical vapor deposition on copper.Carbon177, 282–290 (2021)

    work page 2021

  10. [10]

    Commun.11, 546 (2020)

    Gao, Z.et al.Large-area epitaxial growth of curvature-stabilized ABC trilayer graphene.Nat. Commun.11, 546 (2020)

    work page 2020

  11. [11]

    P., Calandra, M

    Nery, J. P., Calandra, M. & Mauri, F. Long-Range Rhombohedral-Stacked graphene through shear.Nano Lett.20, 5017–5023 (2020). 16

    work page 2020

  12. [12]

    Dey, A., Azizimanesh, A., Wu, S. M. & Askari, H. Uniaxial strain-induced stacking order change in trilayer graphene.ACS Appl. Mater. Interfaces(2024)

    work page 2024

  13. [13]

    & Koskinen, P

    Korhonen, T. & Koskinen, P. Peeling of multilayer graphene creates complex inter- layer sliding patterns.Phys. Rev. B92, 115427 (2015)

    work page 2015

  14. [14]

    P.et al.Anomalous twin boundaries in two dimensional materials.Nat

    Rooney, A. P.et al.Anomalous twin boundaries in two dimensional materials.Nat. Commun.9, 3597 (2018)

    work page 2018

  15. [15]

    Holleis, L.et al.Cryogenic shock exfoliation for ultrahigh mobility rhombohedral graphite nanoelectronics.arXiv(2026)

    work page 2026

  16. [16]

    P., Calandra, M

    Nery, J. P., Calandra, M. & Mauri, F. Ab-initio energetics of graphite and multilayer graphene: stability of bernal versus rhombohedral stacking.2D Mater.8, 035006 (2021)

    work page 2021

  17. [17]

    Commun.12, 242 (2021)

    Halbertal, D.et al.Moiré metrology of energy landscapes in van der waals het- erostructures.Nat. Commun.12, 242 (2021)

    work page 2021

  18. [18]

    Nano Lett.19, 8526–8532 (2019)

    Yang, Y.et al.Stacking order in graphite films controlled by van der waals technology. Nano Lett.19, 8526–8532 (2019)

    work page 2019

  19. [19]

    McEllistrim, A., Garcia-Ruiz, A., Goodwin, Z. A. H. & Fal’ko, V. I. Spectroscopic signatures of tetralayer graphene polytypes.Phys. Rev. B107, 155147 (2023)

    work page 2023

  20. [20]

    Klar, P.et al.Raman scattering efficiency of graphene.Phys. Rev. B: Condens. Matter Mater. Phys.87, 205435 (2013)

    work page 2013

  21. [21]

    Feng, Z.et al.Rapid infrared imaging of rhombohedral graphene.Phys. Rev. Appl. 23, 034012 (2025)

    work page 2025

  22. [22]

    L., Proctor, D

    Blakslee, O. L., Proctor, D. G., Seldin, E. J., Spence, G. B. & Weng, T. Elastic constants of compression-annealed pyrolytic graphite.J. Appl. Phys.41, 3373–3382 (1970). 17

    work page 1970

  23. [23]

    & Chiarello, G

    Politano, A. & Chiarello, G. Probing the Young’s modulus and Poisson’s ratio in graphene/metal interfaces and graphite: a comparative study.Nano Res.8, 1847– 1856 (2015)

    work page 2015

  24. [24]

    A., Lee, J

    Faccinto, J. A., Lee, J. & Kim, K. J. Tensile modeling PVC gels for electrohydraulic actuators.Polymers17, 2641 (2025)

    work page 2025

  25. [25]

    S.et al.Strain solitons and topological defects in bilayer graphene.Proc

    Alden, J. S.et al.Strain solitons and topological defects in bilayer graphene.Proc. Natl. Acad. Sci. U. S. A.110, 11256–11260 (2013)

    work page 2013

  26. [26]

    Science385, 53–56 (2024)

    Yasuda, K.et al.Ultrafast high-endurance memory based on sliding ferroelectrics. Science385, 53–56 (2024)

    work page 2024

  27. [27]

    zrbyte/ramantools: v0.3.1, DOI: 10.5281/zenodo.10143138 (2023)

    Nemes-Incze, P. zrbyte/ramantools: v0.3.1, DOI: 10.5281/zenodo.10143138 (2023). 18

    work page doi:10.5281/zenodo.10143138 2023