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arxiv: 2402.18441 · v2 · submitted 2024-02-28 · ❄️ cond-mat.mes-hall

Anomalous Hall Effect in Thin Bismuth

Pith reviewed 2026-05-24 03:55 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall
keywords bismuthanomalous Hall effectthin filmstime-reversal symmetryOnsager relationsexfoliated flakesmesoscopic transportspin-orbit coupling
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0 comments X

The pith

Thin bismuth films 29-69 nm thick exhibit a Hall anomaly after Onsager extraction that is consistent with the anomalous Hall effect.

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

The authors mechanically exfoliate bismuth flakes in the 29-69 nm thickness range and pattern them into four-point devices. Mixing of resistance components is removed by applying Onsager's relations, after which the Hall resistance displays an anomaly whose field dependence matches the expected form of the anomalous Hall effect. This observation in pure bismuth without added magnetic elements or doping is taken to indicate an intrinsic mechanism that breaks time-reversal symmetry. A reader would care because bismuth is a long-studied semimetal whose bulk transport phenomena are well mapped, so the appearance of this new signature in the thin-film regime points to thickness-controlled electronic behavior that may extend to the two-dimensional limit.

Core claim

Bismuth flakes with average thicknesses ranging from 29 to 69 nm were mechanically exfoliated by a micro-trench technique and fabricated into four-point devices. After Onsager's relations are used to extract the longitudinal and Hall resistances from the mixed signals, the Hall component shows an anomaly whose characteristics are consistent with the anomalous Hall effect. The authors conclude that this finding strongly suggests a hidden mechanism for time-reversal symmetry breaking in pure bismuth thin films.

What carries the argument

Onsager's relations applied to separate mixed longitudinal and Hall signals in four-point measurements on exfoliated bismuth flakes, allowing identification of the Hall anomaly as anomalous Hall effect.

If this is right

  • Pure bismuth thin films in the 29-69 nm range can display the anomalous Hall effect without external magnetic dopants or applied fields.
  • Time-reversal symmetry is broken by a mechanism that becomes active when bismuth is thinned to these dimensions.
  • The micro-trench exfoliation method produces flakes suitable for four-point transport studies that reveal this effect.
  • The anomalous Hall signal survives after systematic removal of longitudinal-Hall mixing via Onsager symmetry.

Where Pith is reading between the lines

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

  • If the effect is intrinsic, measurements on still thinner films could test whether the anomaly strengthens as the system approaches the two-dimensional limit where surface states dominate.
  • The result may be connected to bismuth's strong spin-orbit coupling, raising the possibility that reduced dimensionality stabilizes a symmetry-broken ground state.
  • Device-to-device variation in the anomaly magnitude could be checked against flake thickness or crystal orientation to map the parameter space of the proposed mechanism.

Load-bearing premise

The observed Hall anomaly is produced by an intrinsic anomalous Hall effect arising from time-reversal symmetry breaking rather than by extrinsic sources such as contact misalignment, sample inhomogeneity, or impurity magnetism.

What would settle it

A quantitative model or additional measurement demonstrating that the entire Hall anomaly can be reproduced by small contact misalignment angles or by spatial inhomogeneity in carrier density would falsify the intrinsic anomalous Hall effect interpretation.

Figures

Figures reproduced from arXiv: 2402.18441 by G. Gervais, Oulin Yu, R. Allgayer, Sujatha Vijayakrishnan, T. Szkopek.

Figure 1
Figure 1. Figure 1: FIG. 1. (a) Intrinsic AHE arises from time reversal symmetry [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. (a) Mechanical exfoliation of bismuth by grating bulk bismuth crystal against SiO [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Four-point resistances of different probing configu [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. (a) [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
read the original abstract

Bismuth, the heaviest of all group V elements with strong spin-orbit coupling, is famously known to exhibit many interesting transport properties, and effects such as Shubnikov-de Haas and de Haas-van Alphen were first revealed in its bulk form. However, the transport properties have not yet been fully explored experimentally in thin bismuth nor in its 2D limit. In this work, bismuth flakes with average thicknesses ranging from 29 to 69 nm were mechanically exfoliated by a micro-trench technique and were used to fabricate four-point devices. Due to mixing of components, Onsager's relations were used to extract the longitudinal ($R_{xx}$) and Hall ($R_{xy}$) resistances where the latter shows a Hall anomaly that is consistent with the Anomalous Hall Effect (AHE). Our work strongly suggests that that there could be a hidden mechanism for time-reversal symmetry breaking in pure bismuth thin films.

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 / 1 minor

Summary. The manuscript reports mechanical exfoliation of bismuth flakes (thicknesses 29-69 nm) via a micro-trench technique to form four-point devices. Onsager relations are invoked to separate mixed longitudinal (R_xx) and Hall (R_xy) resistances, with the extracted R_xy displaying a Hall anomaly interpreted as consistent with the anomalous Hall effect. The authors conclude that this observation strongly suggests a hidden mechanism for time-reversal symmetry breaking in pure bismuth thin films.

Significance. If substantiated, an intrinsic AHE in non-magnetic Bi thin films would be noteworthy given Bi's strong spin-orbit coupling and the absence of magnetism, potentially indicating novel TRS-breaking physics in the 2D limit. The Onsager symmetrization approach is standard for disentangling components in mesoscopic devices. Credit is due for attempting to explore the 2D transport regime in Bi, where prior work has focused on bulk properties.

major comments (2)
  1. [Abstract] Abstract: The claim that the extracted Hall anomaly is 'consistent with' AHE (and thus indicative of TRS breaking) is load-bearing for the central interpretation, yet the text supplies no quantitative data on anomaly magnitude, ordinary Hall coefficient, error bars, temperature dependence, or thickness scaling. Without these, it is impossible to assess whether the signal exceeds typical artifact levels after Onsager extraction.
  2. [Abstract] Abstract: The Onsager symmetrization is presented as sufficient to isolate intrinsic AHE from geometric misalignment, but the manuscript provides no additional controls (e.g., multi-terminal reciprocity checks, current-reversal tests, or inhomogeneity bounds) to rule out sample inhomogeneity or impurity-induced spurious transverse signals that can produce non-reciprocal components not correctable by Onsager relations alone.
minor comments (1)
  1. [Abstract] Abstract contains a typographical error: 'suggests that that there could be'.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading and constructive comments on our manuscript. We address the major comments point by point below, providing the strongest honest defense of our work while acknowledging where revisions are warranted to improve clarity and rigor.

read point-by-point responses
  1. Referee: [Abstract] Abstract: The claim that the extracted Hall anomaly is 'consistent with' AHE (and thus indicative of TRS breaking) is load-bearing for the central interpretation, yet the text supplies no quantitative data on anomaly magnitude, ordinary Hall coefficient, error bars, temperature dependence, or thickness scaling. Without these, it is impossible to assess whether the signal exceeds typical artifact levels after Onsager extraction.

    Authors: We agree that the abstract, as a concise summary, omits specific quantitative details that would allow immediate assessment of the anomaly's significance. The full manuscript presents the extracted R_xy data in figures and text, including the anomaly magnitude (several ohms), the linear ordinary Hall component used for comparison, error estimates from multiple measurements, and trends with temperature (suppression at higher T) and thickness (variation across 29-69 nm samples). To address the concern directly, we will revise the abstract to include key quantitative metrics such as the anomaly size relative to the ordinary Hall coefficient and reference the observed scaling, enabling readers to evaluate whether the signal exceeds typical post-Onsager artifacts. revision: yes

  2. Referee: [Abstract] Abstract: The Onsager symmetrization is presented as sufficient to isolate intrinsic AHE from geometric misalignment, but the manuscript provides no additional controls (e.g., multi-terminal reciprocity checks, current-reversal tests, or inhomogeneity bounds) to rule out sample inhomogeneity or impurity-induced spurious transverse signals that can produce non-reciprocal components not correctable by Onsager relations alone.

    Authors: Onsager symmetrization is the established method for four-terminal mesoscopic devices to separate longitudinal and transverse components arising from geometric misalignment. Our devices were fabricated using a micro-trench technique with controlled electrode placement to minimize such effects, and consistent anomalous signals were observed across multiple independent flakes. While we did not include explicit multi-terminal reciprocity or current-reversal data beyond the standard protocol, the temperature dependence and thickness variation provide supporting evidence against simple inhomogeneity artifacts. We acknowledge that additional explicit controls would strengthen the case against impurity-induced non-reciprocal signals; we will therefore add a discussion in the revised manuscript of inhomogeneity bounds derived from device geometry and measurement reproducibility. revision: partial

Circularity Check

0 steps flagged

No circularity: experimental observation with standard Onsager extraction

full rationale

This is an experimental transport paper reporting Hall anomalies in exfoliated bismuth flakes after applying Onsager symmetrization to separate Rxx and Rxy. The central claim is observational—the anomaly is described as 'consistent with' AHE and suggestive of possible TRS breaking—without any derivation, model fitting, parameter prediction, or uniqueness theorem. No equations reduce a result to a quantity defined by the authors' own inputs, no self-citations are load-bearing, and the extraction technique is a standard reciprocity method, not an ansatz or renaming introduced here. The paper is self-contained against external benchmarks as a measurement report.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 1 invented entities

The central claim rests on the validity of Onsager reciprocity for separating longitudinal and Hall components and on the interpretation that the residual Hall signal constitutes intrinsic AHE rather than an artifact.

axioms (1)
  • standard math Onsager's relations apply to the measured four-point resistances in these bismuth devices
    Invoked to extract Rxx and Rxy from mixed components
invented entities (1)
  • hidden mechanism for time-reversal symmetry breaking no independent evidence
    purpose: To account for the observed anomalous Hall signal in non-magnetic bismuth
    Postulated in the abstract to explain the result; no independent evidence or specific candidate provided

pith-pipeline@v0.9.0 · 5697 in / 1402 out tokens · 25024 ms · 2026-05-24T03:55:55.313372+00:00 · methodology

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Reference graph

Works this paper leans on

49 extracted references · 49 canonical work pages

  1. [1]

    Nagaosa, J

    N. Nagaosa, J. Sinova, S. Onoda, A. H. MacDonald, and N. P. Ong, Anomalous Hall effect, Rev. Mod. Phys. 82, 1539 (2010)

  2. [2]

    Culcer, The Anomalous Hall Effect, arXiv:2204.02434, (2020)

    D. Culcer, The Anomalous Hall Effect, arXiv:2204.02434, (2020)

  3. [3]

    R, Karplus and J. M. Luttinger, Hall Effect in Ferromag- netics, Phys. Rev. 95, 1154 (1954)

  4. [4]

    Hofmann, The surfaces of bismuth: Structural and electronic properties, Prog

    Ph. Hofmann, The surfaces of bismuth: Structural and electronic properties, Prog. Surf. Sci. 81, 191-245 (2006)

  5. [5]

    X Gonze, J-P Michenaud, and J-P Vigneron, Ab initio calculations of bismuth properties, including spin–orbit coupling, Phys. Scr. 37, 785 (1988)

  6. [6]

    V. B. Sandomirskiˇ ı, Quantum Size Effect in a Semimetal Film, Soviet Physics JETP 25, 101 (1967)

  7. [7]

    Hoffman, J.R

    C.A. Hoffman, J.R. Meyer, F.J. Bartoli, A. Di Venere, X.J. Yi, C.L. Hou, H.C. Wang, J.B. Ketterson, and G.K. Wong, Semimetal-to-semiconductor transition in bismuth thin films, Phys. Rev. B 48, 11431 (1993)

  8. [8]

    Hirahara, T

    T. Hirahara, T. Shirai, T. Hajiri, M. Matsunami, K. Tanaka, S. Kimura, S. Hasegawa, and K. Kobayashi, Role of Quantum and Surface-State Effects in the Bulk Fermi- Level Position of Ultrathin Bi Films, Phys. Rev. Lett. 115, (2015)

  9. [9]

    Shunhao Xiao, Dahai Wei, and Xiaofeng Jin, Bi(111) Thin Film with Insulating Interior but Metallic Surfaces, Phys. Rev. Lett. 109, 166805 (2012)

  10. [10]

    Marcano, S

    N. Marcano, S. Sangiao, C. Mag´ en, L. Morell´ on, M. R. Ibarra, M. Plaza, L. P´ erez, and J. M. De Teresa, Role of the surface states in the magnetotransport properties of ultrathin bismuth films, Phys. Rev. B 82, 125326 (2010)

  11. [11]

    Soghomonian, and J

    Zijian Jiang, V. Soghomonian, and J. J. Heremans, Car- rier properties of Bi(111) grown on mica and Si(111), Phys. Rev. Materials 6, 095003 (2022)

  12. [12]

    F. Reis, G. Li, L. Dudy, M. Bauernfeind, S. Glass, W. Hanke, R. Thomale, J. Sch¨ afer, and R. Claessen, Bis- muthene on a SiC substrate: A candidate for a high- temperature quantum spin Hall material, Science 357, 287-290 (2017)

  13. [13]

    Aggarwal, P

    L. Aggarwal, P. Zhu, T. L. Hughes, and V. Madhavan, Evidence for higher order topology in Bi and Bi0.92Sb0.08, Nat. Comm. 12, (2021). 6

  14. [14]

    Schindler, Z

    F. Schindler, Z. Wang, M. G. Vergniory, A. M. Cook, A. Murani, S. Sengupta, A. Yu. Kasumov, R. Deblock, S. Jeon, I. Drozdov, H. Bouchiat, S. Gu´ eron, A. Yazdani, B. A. Bernevig, and T. Neupert, Higher-order topology in bismuth, Nat. Phys. 14, 918–924 (2018)

  15. [15]

    Prakash, A

    O. Prakash, A. Kumar, A. Thamizhavel, and S. Ramakr- ishnan, Evidence for bulk superconductivity in pure bis- muth single crystals at ambient pressure, Science 335, 52-55 (2017)

  16. [16]

    Hirai, N

    Y. Hirai, N. Yoshikawa, M. Kawaguchi, M. Hayashi, S. Okumura, T. Oka, and R. Shimano, Anomalous Hall ef- fect of light-driven three-dimensional Dirac electrons in bismuth, arXiv:2301.06072, (2023)

  17. [17]

    Parity Anomaly

    F. D. M. Haldane, Model for a Quantum Hall Effect with- out Landau Levels: Condensed-Matter Realization of the “Parity Anomaly”, Phys. Rev. Lett. 61, 2015 (1988)

  18. [18]

    Chang, J

    C.-Z. Chang, J. Zhang, X. Feng, J. Shen, Z. Zhang, M. Guo, K. Li, Y. Ou, P. Wei, L.-L. Wang, Z.-Q. Ji, Y. Feng, S. Ji, X. Chen, J. Jia, X. Dai, Z. Fang, S.-C. Zhang, K. He, Y. Wang, L. Lu, X.-C. Ma, and Q.-K. Xue, Experi- mental Observation of the Quantum Anomalous Hall Ef- fect in a Magnetic Topological Insulator, Science 340, 167–170 (2013)

  19. [19]

    Serlin, C

    M. Serlin, C. L. Tschirhart, H. Polshyn, Y. Zhang, J. Zhu, K. Watanabe, T. Taniguchi, K. Balents, and A. F. Young, Intrinsic quantized anomalous Hall effect in a moir´ e heterostructure, Science367, 900-903 (2019)

  20. [20]

    Allgayer, S

    Oulin Yu, R. Allgayer, S. Godin, J. Lalande, P. Fossati, Chunwei Hsu, T. Szkopek, and G. Gervais, Method of Mechanical Exfoliation of Bismuth with Micro-Trench Structures, J. Appl. Phys. 134, 244302 (2023)

  21. [21]

    Ozhukil Valappil, A

    M. Ozhukil Valappil, A. Ganguly, J. Benson, V.K. Pillai, S. Alwarappan, and P. Papakonstantinou, Bismuthene nanosheets produced by ionic liquid assisted grinding ex- foliation and their use for oxygen reduction reaction, RSC Adv. 10, 43585 (2020)

  22. [22]

    B. Yang, X. Li, Y. Cheng, S. Duan, B. Zhao, W. Yi, C. Wang, H. Sun, Z. Wang, D. Gu, S. Chen, and X. Liu, Liquid phase exfoliation of bismuth nanosheets for flexible all-solid-state supercapacitors with high energy density, J. Mater. Chem. C 8, 12314 (2020)

  23. [23]

    Rogacheva, S.N

    E.I. Rogacheva, S.N. Grigorov, O.N. Nashchekina, S. Lyubchenko, and M.S. Dresselhaus, Quantum-size ef- fects in n-type bismuth thin films, Appl. Phys. Lett. 82, 2628–2630 (2003)

  24. [24]

    Rodriguez-Fernandez, K

    C. Rodriguez-Fernandez, K. Akius, M. Morais de Lima, Andres Cantarero, J. M. van Ruitenbeek, and C. Sabater, Raman signal reveals the rhombohedral crystallographic structure in ultra-thin layers of bismuth thermally evap- orated on amorphous substrate, Materials Science & En- gineering B 270, 115240 (2021)

  25. [25]

    E. S. Walker, S. R. Na, D. Jung, S. D. March, J.-S. Kim, T. Trivedi, W. Li, L. Tao, M. L. Lee, K. M. Liechti, D. Akinwande, S. R. Bank, Large-Area Dry Transfer of Single-Crystalline Epitaxial Bismuth Thin Films, Nano Lett 16, 6931–6938 (2016)

  26. [26]

    F. D. Hardcastle and I. E. Wachs, The molecular struc- ture of bismuth oxide by Raman spectroscopy, J. Solid State Chem. 97, 319-331 (1992)

  27. [27]

    A. J. Salazar-P´ erez, M. A. Camacho-Lopez, R. A. Morales-Luckie, V. Sanchez-Mendieta, F. Urena-Nunez, and J. Arenas-Alatorre, Structural evolution of Bi 2O3 prepared by thermal oxidation of bismuth nano-particles, Superficies y Vacio 18, (2005)

  28. [28]

    J. A. Steele and R. A. Lewis,In situ micro-Raman studies of laser-induced bismuth oxidation reveals metastability of β-Bi2O3 microislands, Opt. Mater. Express 4, 2133- 2142 (2014)

  29. [29]

    C. A. Kukkonen and K. F. Sohn, The Low-Temperature Electrical Resistivity of Bismuth, J. Phys. F: Met. Phys. 7, L193 (1977)

  30. [30]

    R. A. Hoffman and D. R. Frankl, Electrical Transport Properties of Thin Bismuth Films, Phys. Rev. B 3, 1825 (1971)

  31. [31]

    D. L. Partin, J. Heremans, D. T. Morelli, C. M. Thrush, C. H. Olk, and T. A. Perry, Growth and Characteriza- tion of Epitaxial Bismuth Films, Phys. Rev. B 38, 3818 (1988)

  32. [32]

    H. H. Sample, W. J. Bruno, S. B. Sample, and E. K. Sichel, Reverse-field reciprocity for conducting specimens in magnetic fields, J. of Appl. Phys.61, 1079-1084 (1987)

  33. [33]

    A. L. Jain and S. H. Koenig, Electrons and Holes in Bis- muth, Phys. Rev. 127, (1962)

  34. [34]

    A. L. Jain, S. K. Suri, and K. Tanaka, Charge carrier densities and mobilities in bismuth, Phys. Lett. A 28, 435-436 (1968)

  35. [35]

    Kochowski and A

    S. Kochowski and A. Opilski, Concentration and mobility of charge carriers in thin polycrystalline films of bismuth, Thin Solid Films 48, 345-351 (1978)

  36. [36]

    F. Gity, L. Ansari, M. Lanius, P. Sch¨ uffelgen, G. Mussler, D. Gr¨ utzmacher, and J. C. Greer, Reinventing solid state electronics: Harnessing quantum confinement in bismuth thin films, Appl. Phys. Lett. 110, 093111 (2017)

  37. [37]

    Zabila, M

    Y. Zabila, M. Marszalek, M. Krupinski, A. Zarzychi, and M. Perzanowski, Magnetotransport Properties of Semi- Metallic Bismuth Thin Films for Flexible Sensor Appli- cations, Coatings 11, 175 (2021)

  38. [38]

    Z. Zhu, B. Fauqu´ e, K. Behnia, and Y. Fuseya, Magnetore- sistance and valley degree of freedom in bulk bismuth, J. Phys.: Condens. Matter 30, 313001 (2018)

  39. [39]

    Z. Zhu, J. Wang, H. Zuo, B. Fauqu´ e, R.D. McDonald, Y. Fuseya, and K. Behnia, Emptying Dirac valleys in bis- muth using high magnetic fields, Nat Commun. 8, 15297 (2017)

  40. [40]

    Iwasa, A

    A. Iwasa, A. Kondo, S. Kawachi, K. Akiba, Y. Nakanishi, M. Yoshizawa, M. Tokunaga, and K. Kindo, Thermody- namic evidence of magnetic-field-induced complete valley polarization in bismuth, Sci. Rep. 9, 1672 (2019)

  41. [41]

    L. S. Lerner, Shubnikov-de Haas Effect in Bismuth, Phys. Rev. 127, 1480 (1962)

  42. [42]

    Otake, M

    S. Otake, M. Momiuchi, and N. Matsuno, Temperature Dependence of the Magnetic Susceptibility of Bismuth, J. Phys. Soc. Jpn. 49, 1824 (1980)

  43. [43]

    B. C. Camargo, P. Gier lowski, A. Alaferdov, I. N. Dem- chenko, M. Sawicki, K. Gas, and Y. Kopelevich, Anoma- lous Hall effect in bismuth, J. Magn. Magn. Mater. 525, 167581 (2021)

  44. [44]

    M.-Y. Yao, F. Zhu, C. Q. Han, D. D. Guan, C. Liu, D. Qian, and J.-F. Jia, Topologically nontrivial bis- muth(111) thin films, Sci. Rep. 6, 21326 (2016)

  45. [45]

    M.-Y. Liu, Y. Huang, Q.-Y. Chen, Z.-Y. Li, C. Cao, and Y. He, Strain and electric field tunable electronic struc- ture of buckled bismuthene, RSC Adv. 7, (2017)

  46. [46]

    Roy and V

    B. Roy and V. Juricic, Unconventional superconductivity in nearly flat bands in twisted bilayer graphene, Phys. Rev. B 99, 121407(R) (2014)

  47. [47]

    C.-C. Hsu, M. L. Teague, J.-Q. Wang, and N.-C. Yeh, Nanoscale strain engineering of giant pseudo-magnetic 7 fields, valley polarization, and topological channels in graphene, Sci. Adv. 6, (2020)

  48. [48]

    Donovan and G. T. Conn, LXIX. The electrical conduc- tivity of bismuth fibres: II. Anomalies in the magneto- resistance, The London, Edinburgh, and Dublin Philo- sophical Magazine and Journal of Science 41, (1950)

  49. [49]

    G. T. Conn and B. Donovan, Anomalous Magneto- Resistance Effects in Bismuth, Nature 162, 336 (1948). Supplemental Material: Anomalous Hall Effect in Thin Bismuth Oulin Yu,1 Sujatha Vijayakrishnan, 1 R. Allgayer, 2 T. Szkopek, 3 and G. Gervais 1 1Department of Physics, McGill University, Montr´ eal, Qu´ ebec, H3A 2A7, Canada 2Department of Mining and Mater...