Thermal Diode: One-Way Heat Flow as a Channel Problem (FBA Handles & Pass/Fail)

Mar 4, 2026

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C4 – Quantum Information & Channels (CPTP), C6 – Thermodynamics, Aging & Arrow of Time, C8 – Methods, Data & Reproducibility, Review EN

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6 min read

In https://arxiv.org/abs/2510.13124 (Ghalekohneh & Zhao, preprint 2025), a decomposition of non-reciprocal, far-field radiative heat transfer in multi-body emitter networks is described: the heat current is split into an equilibrium contribution with persistent internal circulation and a non-equilibrium contribution for exchange with the environment; the latter is claimed to be engineerable such that “perfect” thermal rectification and circulation become possible. In https://par.nsf.gov/servlets/purl/10661583 (Phys. Rev. B 113, 2026), the authors also report direction-dependent thermal conductivity mediated by non-reciprocal polaritons in magneto-optical systems and/or Weyl semimetals.

The FBA view turns this into not a device promise, but an operational problem of channel signatures, null tests, and pass/fail: What exactly is “one-way heat” as a measurable quantity, which confounders can imitate it, and which protocol changes yield hard decisions?

Source anchors & subject

Submitted link

https://www.ingenieur.de/technik/fachbereiche/elektronik/physiker-knacken-ein-grundproblem-moderner-elektronik/

Primary sources

https://arxiv.org/abs/2510.13124 (preprint)
https://par.nsf.gov/servlets/purl/10661583 (journal PDF)

Reality check

Standard/established: In the model framework of the preprint, non-reciprocity is used as a key ingredient to obtain, besides net exchange, an internally circulating radiative power at equilibrium (multi-body geometry, far-field).
Standard/established: The companion study formulates direction-dependent heat conduction as a transport signature of non-reciprocal polaritons (material choice + protocol knob via magnetic field).
Hypothesis: The device relevance sketched in press pieces (chips/batteries/space) hinges on integration details: achievable flux contrasts, parasitic heat paths, field strengths, material losses, and measurement systematics.

FBA view

Handle: Treat “heat between components” as a network of directed process channels (composition; comparison of two protocols: forward vs backward). (Definition III.4.1.1)
Principle: “One-way” is, at its core, an arrow statement: unselected processing may only decrease certain distinguishabilities; that becomes usable as a protocol test rather than as a story. (Definition I.5.3.1)
Proxy: Replace superlatives with a calibration curve: a rectification metric as a function of temperature bias, magnetic field, and geometry (with an error band as part of the claim).
Proxy: Require for every “thermal logic” a budget bookkeeping over entropy production as the direct cost/irreversibility measure. (Definition VIII.6.1.1)
Principle: If the setting is used in a reset/erasure-like way (thermo-logic), a Landauer lower bound must run as a pass/fail check; otherwise the efficiency claim is underdetermined. (Corollary VIII.6.1.2)
Residual: Use symmetry checks (odd/even under field reversal) as a systematics filter before claiming “new physics” or “perfection.” (Lemma VIII.9.1.1)

New insights from FBA

FROM→TO: “Thermal diode as a component” → “protocol pair with shared calibration” (same thermometry, same geometry; only the protocol knob changes). Implicit assumption: forward/backward do not differ by hidden re-calibration (e.g., sensor drift in field).
FROM→TO: “circulator” → “loop observable” (edge powers in a triangle rather than only net outflow). Implicit assumption: edge-resolved measurement is possible without the probes themselves shorting out the loop.
FROM→TO: “non-reciprocity explains everything” → “signature family under field reversal” (direction swap as a minimal identity test). Implicit assumption: field reversal inverts the relevant non-reciprocal contribution more strongly than it changes parasitic heat paths.
FROM→TO: “thermal management” → “budget pipeline” (flux contrast, stability over time, entropy cost, systematics budget). Implicit assumption: there is clean accounting of which dissipation is classified as internal vs external.

Clarification / improvement with FBA

Confounder: Parasitic heat conduction through mounts, wires, or residual gas can fake or mask a “radiative diode” effect; this must be budgeted separately.
Confounder: Magnetic-field-dependent thermometry (Seebeck/Hall effects, sensor offsets) can create apparent directional asymmetries; field sweeps require blind/null channels.
Control idea: Triple control: field off, field reversed, and sample geometrically mirrored (hot/cold swapped)—only if all three are consistent does the asymmetry count as a non-reciprocal signature.
Control idea: Separate “exchange with environment” from “internal loop” via a multi-node design: identical boundary conditions, but additional node measurement (energy conservation per edge as a cross-check).
Proxy: Report not just “large/small,” but a reproducibility curve: rectification metric vs temperature bias and time (drift/aging of emissivity as its own channel in the systematics budget).

Alternative readings & conclusions

Hypothesis: An observed “one-way” contrast stems primarily from anisotropic emissivity or view-factor asymmetry, not from genuine non-reciprocity; then the signature should follow geometric mirroring even without changing the field.
open/unclear: The claimed persistent equilibrium circulation could depend strongly on ideal assumptions (material models, far-field approximations, environment model); without a parameter register, transferability to real platforms is underdetermined.
FBA: “Circulation” becomes its own physical claim only once the bookkeeping cleanly separates the environment channel; otherwise it is a relabeling of a hidden exchange path that should show up in a residual/null test. (Definition VIII.6.1.1)

Tests/Experiments (Pass/Fail) with an FBA touch

Pass/Fail (Standard/established): rectification metric of radiative power | vacuum setup, two surfaces, temperature bias in both directions, field sweep | clear asymmetry beyond error band, with consistent field dependence | symmetry within the error band or drift dominates the signal
Null test (FBA): field-reversal signature (direction swap) | same sample, identical thermometry, measurement at +B and −B | forward/backward roles swap consistently, without additional re-calibration | no direction swap or a strong sensor offset correlates with field
Residual (open/unclear): loop observable at equilibrium (internal circulation) | triangular multi-node, equal temperatures, edge-resolved power balance | nontrivial loop power with simultaneously small net environment exchange | loop vanishes after background/parasitic subtraction or is explainable only via leakage paths
Pass/Fail (Standard/established): directional difference of thermal conductivity in a solid | transport measurement along + and − direction, field on/off, material platform as in the primary source | directional difference appears with field and vanishes without field | directional difference persists without field or tracks thermometry asymmetry

Added value of the FBA view

Added value: 8/10 – The post translates “one-way heat” into testable signatures (protocol pair, field reversal, loop observable) and forces, via confounders and budget quantities, clear pass/fail decisions instead of device promises.