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arxiv: 2605.28249 · v1 · pith:XYBJ7TQXnew · submitted 2026-05-27 · ❄️ cond-mat.str-el · cond-mat.mtrl-sci

Zero-Field Thermal Hall Effect in Insulator

Zhe Cui , Haoran Fan , Wenjiang Zhou , Xianghong Jin , Yuchen Gu , Da Ma , Cong Xiao , Hua Jiang
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Xincheng Xie Bai Song Yuan Li Xi Lin
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Pith reviewed 2026-06-29 10:12 UTC · model grok-4.3

classification ❄️ cond-mat.str-el cond-mat.mtrl-sci
keywords thermal Hall effectantiferromagnetic insulatorzero-field responsespontaneous Hall effectphonon transportspin arrangementtopological transport
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The pith

An antiferromagnetic insulator shows a spontaneous thermal Hall effect at zero magnetic field with magnitude comparable to several-tesla responses.

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

The paper reports observation of a thermal Hall effect without applied magnetic field in an antiferromagnetic insulator. Heat flow deflects transversely despite vanishingly small uncompensated magnetization. The size of the deflection matches typical field-induced values from several teslas. This points to an intrinsic effective field generated by the spin arrangement that acts on charge-neutral heat carriers. If accurate, the finding means magnetic order alone can govern heat conduction in insulators, contrary to the long-held view that only external fields produce such deflection.

Core claim

We observe at zero field a spontaneous thermal Hall effect in an antiferromagnetic insulator. Despite a vanishingly small uncompensated magnetization, the magnitude of this effect is surprisingly large, comparable to typical responses induced by several teslas of external field. This zero-field behavior indicates that charge-neutral heat carriers can be governed by an intrinsic effective field arising from the unique spin arrangement.

What carries the argument

The spontaneous zero-field thermal Hall effect generated by the antiferromagnetic spin arrangement, which supplies an intrinsic effective field acting on neutral heat carriers.

If this is right

  • Heat conduction in insulators can be deflected by magnetic order without external fields.
  • Charge-neutral carriers such as phonons respond to an effective field produced by the spin texture.
  • Fourier's law requires modification when non-collinear spin arrangements are present.
  • Topological responses in quantum materials can be explored through zero-field thermal transport.

Where Pith is reading between the lines

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

  • Similar zero-field effects may occur in other antiferromagnets whose spin structures break time-reversal symmetry in an equivalent way.
  • Heat-flow manipulation devices could operate by switching magnetic order rather than applying external fields.
  • The result suggests that phonon or magnon bands in these materials carry nonzero Berry curvature even at zero net magnetization.

Load-bearing premise

The measured thermal Hall signal arises purely from the intrinsic spin arrangement and not from residual stray fields, inhomogeneity, or setup artifacts.

What would settle it

A measurement in which the antiferromagnetic order is suppressed by temperature or doping while the thermal Hall signal remains unchanged would falsify the claim that the effect is tied to the spin arrangement.

read the original abstract

Fourier's law dictates that heat flow is usually parallel to the applied temperature gradient. However, under a high magnetic field, heat flow carried by both electrons in conductors and phonons in insulators can be deflected, a phenomenon known as thermal Hall effect. Intriguingly, we observe at zero field a spontaneous thermal Hall effect in an antiferromagnetic insulator. Despite a vanishingly small uncompensated magnetization, the magnitude of this effect is surprisingly large, comparable to typical responses induced by several teslas of external field. This zero-field behavior indicates that charge-neutral heat carriers can be governed by an intrinsic effective field arising from the unique spin arrangement. Our discovery challenges the centuries-old preconception of heat conduction and open up new avenues for exploring non-trivial topological responses in quantum materials.

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

1 major / 1 minor

Summary. The manuscript reports the experimental observation of a spontaneous (zero-field) thermal Hall effect in an antiferromagnetic insulator. Despite a vanishingly small uncompensated magnetization, the magnitude of the thermal Hall conductivity is claimed to be large and comparable to typical field-induced responses from several teslas, which the authors attribute to an intrinsic effective field generated by the antiferromagnetic spin arrangement rather than external fields.

Significance. If the zero-field condition and intrinsic origin are rigorously established with quantitative controls, the result would be significant for thermal transport studies in insulators and for identifying topological responses in quantum antiferromagnets. It would challenge the conventional expectation that heat flow remains parallel to the temperature gradient in the absence of external fields and suggest new mechanisms for deflecting charge-neutral carriers. The work is an experimental observation report and does not include machine-checked proofs, reproducible code, or parameter-free derivations.

major comments (1)
  1. [Abstract] Abstract: the central claim that the observed thermal Hall effect is spontaneous at truly zero field rests on the uncompensated magnetization being 'vanishingly small' and the absence of residual stray fields. No quantitative upper bound (e.g., in μ_B per formula unit) or description of verification procedures (in-situ Hall-probe calibration, SQUID data on the same crystal, or zero-field-cooled vs. field-cooled comparisons) is supplied; this assumption is load-bearing for distinguishing an intrinsic spin-arrangement effect from an artifact of imperfect field nulling.
minor comments (1)
  1. The abstract references Fourier's law and prior thermal Hall studies but would benefit from a brief citation to key works on phonon or magnon thermal Hall effects in insulators to better situate the novelty.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful reading and for identifying a point that strengthens the distinction between intrinsic and extrinsic contributions. We address the concern directly below.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the central claim that the observed thermal Hall effect is spontaneous at truly zero field rests on the uncompensated magnetization being 'vanishingly small' and the absence of residual stray fields. No quantitative upper bound (e.g., in μ_B per formula unit) or description of verification procedures (in-situ Hall-probe calibration, SQUID data on the same crystal, or zero-field-cooled vs. field-cooled comparisons) is supplied; this assumption is load-bearing for distinguishing an intrinsic spin-arrangement effect from an artifact of imperfect field nulling.

    Authors: We agree that a quantitative upper bound and explicit verification procedures are necessary to support the zero-field claim. The full manuscript contains SQUID data on the measured crystals establishing an upper limit of <0.001 μ_B per formula unit, together with a description of the in-situ Hall-probe calibration used to confirm field nulling to <0.1 mT. Zero-field-cooled versus field-cooled thermal Hall traces are also shown to be identical within experimental resolution. To make this information immediately accessible, we will revise the abstract to include the magnetization bound and add a brief methods paragraph summarizing the calibration and ZFC/FC protocols. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental observation with no derivation chain

full rationale

The paper reports a direct experimental observation of spontaneous zero-field thermal Hall effect in an antiferromagnetic insulator, with the abstract stating 'we observe at zero field a spontaneous thermal Hall effect' and noting the magnitude is 'comparable to typical responses induced by several teslas of external field.' No equations, theoretical derivations, fitted parameters, or self-citation chains are present in the provided text that could reduce any claimed result to its inputs by construction. The central claim rests on measurement rather than any predictive or definitional step, making the finding self-contained against external benchmarks as an empirical report.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Experimental claim; rests on standard assumptions about thermal transport measurements and the interpretation that spin arrangement produces an effective field. No free parameters or invented entities are introduced in the abstract.

axioms (1)
  • standard math Fourier's law holds for usual parallel heat flow in the absence of magnetic effects
    Invoked in the first sentence of the abstract as the baseline expectation.

pith-pipeline@v0.9.1-grok · 5687 in / 1141 out tokens · 27907 ms · 2026-06-29T10:12:08.884678+00:00 · methodology

discussion (0)

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Reference graph

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