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arxiv: 2604.26168 · v1 · submitted 2026-04-28 · ❄️ cond-mat.mtrl-sci

Negative magnetoresistance in strained α-Sn and α-SnGe films in an in-plane magnetic field

Sunny Phan (1) , Andrei Kogan (1) , Jesse Thompson (2 , 3) , Trent Johnson (2 , Alexander Khaetskii (4) , Arnold Kiefer (3) ((1) Department of Physics , Astronomy
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University of Cincinnati Cincinnati OH USA (2) KBR Beavercreek Township OH USA (3) Air Force Research Laboratory Wright-Patterson AFB (4) Department of Physics Ohio University Athens USA)
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Pith reviewed 2026-05-07 12:22 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci
keywords negativefilmsstrainedalphaanomalychiraldiracfield
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The pith

Negative magnetoresistance occurs in strained alpha-Sn and alpha-SnGe films for both Dirac semimetal and 3D topological insulator states with differing B-field dependence, inconsistent with the chiral anomaly.

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

The study grew thin films of alpha-tin and a tin-germanium mix under strain on substrates. These films were prepared so one set stayed in a Dirac semimetal state while the alloy set entered a three-dimensional topological insulator state. Researchers then passed current through the films while applying a magnetic field parallel to the film plane and measured how resistance changed. They saw resistance drop when the field was turned on, whether the current flowed along the field or across it. The size of the drop depended on field strength differently in the two types of films. This pattern does not match the expected signature of the chiral anomaly, a quantum effect predicted for certain semimetals when electric and magnetic fields align. Instead the data point to other scattering or localization processes. The authors note that film quality, strain uniformity, and contact design can produce similar-looking signals and may explain why earlier reports on alpha-tin films reached conflicting conclusions.

Core claim

Our results are inconsistent with the chiral anomaly and suggest that other mechanisms may be responsible for negative MR in the Dirac/Weyl semimetal phase of α-Sn.

Load-bearing premise

That the observed negative MR arises from intrinsic properties of the identified Dirac semimetal and topological insulator states rather than from sample imperfections, strain inhomogeneity, or measurement artifacts, as the authors themselves flag in their discussion of sample design and material quality.

read the original abstract

To test the hypothesis that the chiral anomaly is responsible for negative magnetoresitance (MR) in \atn{}, we have studied magnetotransport in strained, epitaxial films of pure \aSn{} and the alloy \aSnGe{} that are in the Dirac semimetal and 3D topological insulator state, respectively. We have observed for both states a negative MR with current either parallel or transverse to the in-plane magnetic field, but with a different dependence of MR on $\vec{B}$ strength. Our results are inconsistent with the chiral anomaly and suggest that other mechanisms may be responsible for negative MR in the Dirac/Weyl semimetal phase of \aSn{}. We also discuss several factors in sample design and material quality that may be contributing to the incongruous observations of MR reported in studies of strained \atn{} 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.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on correct identification of the Dirac semimetal and topological insulator states in the strained films and on the assumption that negative MR is not dominated by extrinsic effects.

axioms (1)
  • domain assumption Standard assumptions of uniform current flow and negligible contact resistance in magnetotransport measurements.
    Implicit when interpreting MR sign and magnitude as material properties.

pith-pipeline@v0.9.0 · 5543 in / 1208 out tokens · 71400 ms · 2026-05-07T12:22:53.689711+00:00 · methodology

discussion (0)

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