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Room temperature Planar Hall effect in nanostructures of trigonal-PtBi2
by Arthur Veyrat, Klaus Koepernik, Louis Veyrat, Grigory Shipunov, Iryna Kovalchuk, Saicharan Aswartham, Jiang Qu, Ankit Kumar, Michele Ceccardi, Federico Caglieris, Nicolás Pérez Rodríguez, Romain Giraud, Bernd Büchner, Jeroen van den Brink, Carmine Ortix, Joseph Dufouleur
Submission summary
| Authors (as registered SciPost users): | Nicolas Perez · Arthur Veyrat |
| Submission information | |
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| Preprint Link: | https://arxiv.org/abs/2410.12596v3 (pdf) |
| Date submitted: | Oct. 28, 2025, 12:02 p.m. |
| Submitted by: | Arthur Veyrat |
| Submitted to: | SciPost Physics |
| Ontological classification | |
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| Academic field: | Physics |
| Specialties: |
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| Approach: | Experimental |
Abstract
Trigonal-PtBi2 has recently garnered significant interest as it exhibits unique superconducting topological surface states due to electron pairing on Fermi arcs connecting bulk Weyl nodes. Furthermore, topological nodal lines have been predicted in trigonal-PtBi2, and their signature was measured in magnetotransport as a dissipationless, i.e. odd under a magnetic field reversal, anomalous planar Hall effect. Understanding the topological superconducting surface state in trigonal-PtBi2 requires unravelling the intrinsic geometric properties of the normal state electronic wavefunctions and further studies of their hallmarks in charge transport characteristics are needed. In this work, we reveal the presence of a strong dissipative, i.e. even under a magnetic field reversal, planar Hall effect in PtBi2 at low magnetic fields and up to room temperature. This robust response can be attributed to the presence of Weyl nodes close to the Fermi energy. While this effect generally follows the theoretical prediction for a planar Hall effect in a Weyl semimetal, we show that it deviates from theoretical expectations at both low fields and high temperatures. We also discuss the origin of the PHE in our material, and the contributions of both the topological features in PtBi2 and its possible trivial origin. Our results strengthen the topological nature of PtBi2 and the strong influence of quantum geometric effects on the electronic transport properties of the low energy normal state.
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- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Author comments upon resubmission
We have also provided a point-by-point response to the comments of the reviewers on the previously submitted version.
List of changes
- The discussion on the possible relative importance of the different topological features to the PHE was shifted to the supplementary materials (SM), to focus on the main point of the manuscript and avoid possible confusion.
- At the request of a reviewer, additional information was added to the SM, adapted (with permission) from our previous publications, to centralize information as much as feasible.
- Details were added to the description of the PHE to make explicit that, despite its name, the PHE is not associated with a Lorentz force. -Minor typos were corrected.
Current status:
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I would like to thank the authors for addressing my previous queries. I appreciate the differences between their study and the previous work from PRB 110, 125148 (2024). I also acknowledge that more extensive transport measurements are reported in the present case compared to earlier studies. However, I still do not understand which features make the authors believe that their data "strengthen the topological nature of PtBi2". I found the corresponding part of the reply rather obscure, and I can not support the chosen wording "the measurements are entirely consistent with the prediction of Weyl topology", because it obviously works in the other direction too. The measurements are entirely consistent with the anisotropic orbital magnetoresistance scenario as well.
Two additional reasons for my doubts are some recent publications on t-PtBi2:
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[Appl. Phys. Lett. 126, 233101 (2025)] from June 2025 argues for the Fermi surface anisotropy as the origin of the Hall response
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[Phys. Rev. Materials 9, 084202 (2025)] reports Hall and Nernst effect on single crystals. This paper contains explicit statements against the role of topology in t-PtBi2. For example: "Weyl nodes are a natural source of Berry curvature... and explain ANE contribution even in nonmagnetic compounds such as Cd3As2 and TaP. Although a similar mechanism cannot be completely excluded a priori in PtBi2, our material presents substantial differences with respect to the mentioned cases". The behavior of PtBi2 is then attributed to a "multiband picture" and not to the Weyl nodes.
The authors of that paper further argue that "Weyl nodes in t-PtBi2 are predicted to be located at about 47 meV above the Fermi level, which may be too far to make them dominate the Nernst effect with an anomalous component". Why would the very same Weyl nodes determine the Hall effect but play no role in the Nernst effect of the material?
The aforementioned paper concludes with the statement "...our study does not reveal any evident contribution related to nontrivial topology". Ironically, some of the present authors are co-authors of that paper too.
While the present manuscript on the planar Hall effect in t-PtBi2 contains potentially interesting data, I can not support its publication because it would only lead to a major confusion. Unless I am missing something, the authors seem to have chosen an opportunistic approach and make inconsistent statements regarding the role of topology in the material. I do not think that community would benefit from such a series of mutually contradicting scenarios of t-PtBi2.
Recommendation
Ask for major revision
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“The fact that RRR is strongly thickness dependent” is widespread among metallic solids. It not only implies that the electronic mean free path in nanoflakes is much shorter than in bulk samples but that the path of charge carriers is less controlled. This opens the way for what the investigators of bulk transport in layered conductors call “c-axis contamination”.
Figure 17 of the present version reveals that even the temperature dependence of zero-field resistance in these low RRR samples is not reproducible.
How can one base any solid conclusion by studying these samples?
R _xx and R_xy oscillations (seen in Fig.2j,k,l) have similar amplitudes. This can happen if an electric current with uncontrolled orientation generates tan electric field of similar amplitude in the two channels. with a small shift between them.
This interpretation is backed by the comparison shown in Figure 5 of PRB 110, 125148 (2024). The bulk sample shows a significant magnetoresistance with visible structure as expected in a metal with a non-spherical Fermi surface and reasonably mobile carriers. In contrast, the nanoflakes show small featureless magnetoresistance and their Hall resistivity mirrors the weak magnetoresistance.
If the "room temperature planar Hall effect" is a genuine feature why should it disappear in cleaner samples?
Occam’s razor invites us to look for the simplest available explanation of any observation.
Recommendation
Reject