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arxiv: 2509.09668 · v1 · submitted 2025-09-11 · ❄️ cond-mat.mes-hall · cond-mat.dis-nn

Magnetotransport across Weyl semimetal grain boundaries

Haoyang Tian , Vatsal Dwivedi , Adam Yanis Chaou , Maxim Breitkreiz This is my paper

Pith reviewed 2026-05-18 17:19 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall cond-mat.dis-nn
keywords Weyl semimetalsgrain boundariesmagnetoconductanceFermi arcsdisordertunnel transporttopological interfaces
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The pith

Disorder at the interface between Weyl semimetals does not eliminate the linear increase of tunnel conductance with magnetic field above a crossover strength.

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 universal linear dependence of tunnel magnetoconductance on magnetic field across clean Weyl semimetal interfaces survives interface disorder. This linear behavior holds for fields stronger than a characteristic value B_arc set by equating the time for Lorentz-force traversal of a Fermi arc to the average time between scattering events from one arc to another. Below B_arc the conductance slope instead follows from the numbers of Weyl nodes in each material as N_L N_R over their sum. The linearity's robustness to disorder offers an account for the negative linear magnetoresistance seen in polycrystalline Weyl semimetals. With longer-range correlated disorder the crossover field drops exponentially.

Core claim

A clean interface between two Weyl semimetals features a universal, field-linear tunnel magnetoconductance of (e^2/h) N_ho per magnetic flux quantum, where N_ho is the number of chirality-preserving topological interface Fermi arcs. The linearity remains robust to interface disorder. The slope changes at B_arc where the Lorentz traversal time equals the mean inter-arc scattering time. Above this field the conductance is unaffected by disorder while below it the slope becomes N_L N_R / (N_L + N_R). For correlated disorder potentials B_arc falls exponentially with correlation length.

What carries the argument

The crossover field B_arc defined by equality of the Lorentz-force Fermi-arc traversal time and the mean inter-arc scattering time, which separates the disorder-unaffected high-field regime from the low-field regime governed by node counts.

If this is right

  • For fields much larger than B_arc the magnetoconductance slope stays set by the number of chirality-preserving Fermi arcs N_ho even with disorder.
  • For fields much smaller than B_arc the slope is instead set by the fraction N_L N_R / (N_L + N_R) of left and right Weyl-node pairs.
  • Increasing the spatial correlation length of disorder potentials reduces the crossover field B_arc exponentially.
  • This accounts for the observed robustness of negative linear magnetoresistance in grained Weyl semimetals.

Where Pith is reading between the lines

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

  • Experiments could extract the number of topological interface arcs by measuring the high-field slope of magnetoconductance across engineered grain boundaries.
  • Varying the disorder correlation length through sample preparation would allow shifting the accessible field range for the universal regime.
  • The time-scale comparison mechanism may generalize to transport across other topological interfaces with arc-like states.

Load-bearing premise

A well-defined mean inter-arc scattering time can be identified and compared directly to the Lorentz-force traversal time along the Fermi arc.

What would settle it

Observation of a kink or change in the slope of conductance versus magnetic field at the field strength where the estimated arc traversal time matches the scattering time would support the crossover picture; absence of such a feature would challenge it.

Figures

Figures reproduced from arXiv: 2509.09668 by Adam Yanis Chaou, Haoyang Tian, Maxim Breitkreiz, Vatsal Dwivedi.

Figure 3
Figure 3. Figure 3: FIG. 3. (a) Conductance [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. (a) Transmission [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Conductance of weakly coupled interfaces (exhibit [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Overlap of Fermi-arc wavefunctions [PITH_FULL_IMAGE:figures/full_fig_p010_6.png] view at source ↗
read the original abstract

A clean interface between two Weyl semimetals features a universal, field-linear tunnel magnetoconductance of $(e^2/h)N_\mathrm{ho}$ per magnetic flux quantum, where $N_\mathrm{ho}$ is the number of chirality-preserving topological interface Fermi arcs. In this work we show that the linearity of the magnetoconductance is robust with to interface disorder. The slope of the magnetoconductance changes at a characteristic field strength $B_\mathrm{arc}$ -- the field strength for which the time taken to traverse the Fermi arc due to the Lorentz force is equal to the mean inter-arc scattering time. For fields much larger than $B_\mathrm{arc}$, the magnetoconductance is unaffected by disorder. For fields much smaller than $B_\mathrm{arc}$, the slope is no longer determined by $N_\mathrm{ho}$ but by the simple fraction $N_\mathrm{L} N_\mathrm{R}/(N_\mathrm{L}+N_\mathrm{R})$, where $N_\mathrm{L}$ and $N_\mathrm{R}$ are the numbers of Weyl-node pairs in the left and right Weyl semimetal, respectively. We also consider the effect of spatially correlated disorder potentials, where we find that $B_\mathrm{arc}$ decreases exponentially with increasing correlation length. Our results provide a possible explanation for the recently observed robustness of the negative linear magnetoresistance in grained Weyl semimetals.

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 / 3 minor

Summary. The manuscript analyzes magnetotransport across interfaces between two Weyl semimetals, modeling grain boundaries. It claims that a clean interface supports a universal field-linear tunnel magnetoconductance of (e²/h) N_ho per flux quantum, with N_ho the number of chirality-preserving topological interface Fermi arcs. The central result is that this linear dependence remains robust against interface disorder: a crossover field B_arc is defined by equating the Lorentz-force traversal time along an interface Fermi arc to the mean inter-arc scattering time; for B ≫ B_arc the slope is unaffected by disorder and fixed by N_ho, while for B ≪ B_arc the slope reduces to the fraction N_L N_R / (N_L + N_R). Spatially correlated disorder is shown to reduce B_arc exponentially with correlation length. The findings are offered as an explanation for the robustness of negative linear magnetoresistance observed in grained Weyl semimetals.

Significance. If the semiclassical timescale argument holds, the work supplies a physically transparent account of how topological interface arcs can protect linear magnetoconductance against disorder, offering a possible resolution for experimental reports of robust negative linear magnetoresistance in polycrystalline Weyl samples. The clean separation into disorder-unaffected (high-B) and disorder-affected (low-B) regimes, together with the explicit treatment of correlated potentials, adds practical relevance. The absence of free parameters in the high-field slope and the direct link to Fermi-arc topology are notable strengths of the approach.

major comments (2)
  1. [Discussion of B_arc and the timescale argument (around the definition of the crossover field)] The mean inter-arc scattering time is introduced as a single, momentum-independent quantity whose value is directly compared to the Lorentz traversal time to locate B_arc. No explicit microscopic derivation or disorder-averaged scattering-rate calculation is supplied to establish that this mean remains well-defined and uniform near the nodes under the modeled interface disorder. Because the claimed sharp regime boundary and the universality of the high-field slope both rest on this comparison, the assumption is load-bearing for the central claim.
  2. [Results section on disorder robustness] The manuscript relies entirely on the semiclassical picture without presenting a microscopic conductance calculation (e.g., via Landauer-Büttiker or Kubo formalism) or numerical checks for a concrete disorder realization. Such verification would be needed to confirm that the high-field slope indeed saturates at the value fixed by N_ho once B exceeds B_arc.
minor comments (3)
  1. [Abstract] The abstract contains the typographical error 'robust with to interface disorder'; it should read 'robust with respect to interface disorder'.
  2. [Introduction and abstract] The symbol N_ho is used before its explicit definition as the number of chirality-preserving topological interface Fermi arcs; a brief parenthetical or reference to a schematic figure would improve readability.
  3. [Introduction] A short discussion of how the present semiclassical treatment relates to prior works on Fermi-arc transport or grain-boundary scattering in Weyl semimetals would help situate the novelty.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the constructive comments. We address the two major comments point by point below, indicating where we agree that clarification or additional discussion is warranted.

read point-by-point responses

  1. Referee: The mean inter-arc scattering time is introduced as a single, momentum-independent quantity whose value is directly compared to the Lorentz traversal time to locate B_arc. No explicit microscopic derivation or disorder-averaged scattering-rate calculation is supplied to establish that this mean remains well-defined and uniform near the nodes under the modeled interface disorder. Because the claimed sharp regime boundary and the universality of the high-field slope both rest on this comparison, the assumption is load-bearing for the central claim.

    Authors: We agree that the mean inter-arc scattering time is introduced phenomenologically as an effective parameter in the semiclassical model. It represents the typical time scale for disorder-induced scattering between distinct interface Fermi arcs and is assumed to be roughly uniform for states near the Weyl nodes. While a full microscopic, disorder-averaged scattering-rate calculation from a specific potential would provide more rigor, such a calculation would depend on microscopic details of the disorder that are not specified in the model. The central robustness result for B ≫ B_arc follows from the topological protection of the arcs once the Lorentz traversal time becomes shorter than any finite scattering time; the precise value of that time only sets the location of the crossover. In the revised version we will add a brief paragraph explaining the physical motivation for treating the scattering time as a single effective parameter and its relation to the interface disorder strength. revision: partial

  2. Referee: The manuscript relies entirely on the semiclassical picture without presenting a microscopic conductance calculation (e.g., via Landauer-Büttiker or Kubo formalism) or numerical checks for a concrete disorder realization. Such verification would be needed to confirm that the high-field slope indeed saturates at the value fixed by N_ho once B exceeds B_arc.

    Authors: We acknowledge that a full quantum transport calculation would constitute stronger evidence. Our work employs a semiclassical Boltzmann transport description that directly incorporates the Lorentz force acting on the chiral interface arcs. In the high-field regime the cyclotron radius becomes small compared with the spatial extent of the interface, and the topological character of the arcs precludes backscattering, fixing the slope at (e²/h) N_ho per flux quantum independent of disorder. Performing a microscopic Landauer-Büttiker or Kubo calculation for a disordered multi-arc interface is numerically demanding and lies outside the scope of the present semiclassical analysis. We will add a short discussion of the regime of validity of the semiclassical approximation and the conditions under which the high-field slope is expected to remain protected. revision: partial

Circularity Check

0 steps flagged

No significant circularity; regime crossover defined by independent timescales

full rationale

The paper defines the crossover field B_arc explicitly as the point where Lorentz-force arc traversal time equals mean inter-arc scattering time, then uses this to separate high-field (disorder-unaffected, slope fixed by N_ho) and low-field (slope N_L N_R/(N_L+N_R)) regimes. This is a conventional physical comparison of two distinct timescales rather than a self-definitional loop or fitted parameter renamed as prediction. No equations are shown reducing the claimed universality or linearity robustness to the input data or to a self-citation chain; the result follows from the topological interface arcs and the stated regime separation under the model's assumptions. The derivation remains self-contained without load-bearing self-citations or ansatz smuggling.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The claim rests on the standard topological property that Weyl-semimetal interfaces host chirality-preserving Fermi arcs and on a semiclassical picture that equates two independent timescales to locate a crossover field.

axioms (1)
  • domain assumption Weyl semimetals host chirality-preserving topological Fermi arcs at interfaces between regions of opposite chirality.
    Invoked to define N_ho and the clean-interface conductance; standard from bulk Weyl topology.

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Reference graph

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