REVIEW 4 major objections 3 minor 1 cited by
Thermoelectricity evidence for quantum criticality in clean infinite-layer nickelate films
T0 review · 4 major / 3 minor · reviewed 2026-08-05 · deepseek-v4-flash
Pith's one-line read The paper claims that clean infinite-layer nickelate films sit at an antiferromagnetic quantum critical point, visible in the thermopower as a logarithmic $S/T$ divergence and a ~25 K magnetic-order hump.
desk verdict New transport data in nickelate films that look like quantum criticality, but the interpretation is less secure than the title suggests. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central observable is the thermopower normalized by temperature, $S/T$: its logarithmic divergence as $T \to 0$ is the paper's transport fingerprint for quantum critical antiferromagnetic fluctuations. The ~25 K hump in $S/T$ is identified as the onset of short-range antiferromagnetic order, with supporting evidence from the fourfold symmetry breaking of the in-plane angular magnetoresistance below that temperature. Disorder is the control parameter: increasing disorder flattens $S/T$ and suppresses the critical signatures, which the paper interprets as a transition from band-structure-dominated transport to quantum-critical-dominated transport.
What would settle it
A decisive check would be to measure $S/T$, magnetoresistance, and a direct magnetic probe such as neutron scattering or muon-spin rotation on the same clean film: if no short-range antiferromagnetic order exists below 25 K, or if the logarithmic $S/T$ divergence remains when the putative magnetic order is suppressed by magnetic field or doping, the quantum-critical attribution fails. A phonon-drag test would look for an isotope effect or a thermal-conductivity correlation in the size and temperature dependence of the 25 K hump.
Extended reading notes
Core claim
The central claim is that clean infinite-layer nickelate films are at or near an antiferromagnetic quantum critical point, and that the thermoelectric response provides a direct signature of that criticality. Concretely, the paper reports that the Seebeck coefficient divided by temperature, $S/T$, grows logarithmically as temperature decreases in clean films, while a disordered NdNiO$_2$ film shows a flat $S/T$; a hump appears near 25 K in the clean films, and angular magnetoresistance below that temperature shows fourfold symmetry breaking attributed to short-range antiferromagnetic order. The same logarithmic $S/T$ divergence is then found in a clean superconducting Sm$_{0.73}$Ca$_{0.05}$E
Load-bearing premise
The argument presupposes that the logarithmic $S/T$ divergence and the ~25 K hump are quantum critical antiferromagnetic signatures rather than non-critical effects such as phonon drag or magnetic-impurity scattering.
Editorial extensions
If this is right
- Clean infinite-layer nickelate films exhibit cuprate-like quantum critical transport over a wide doping range, not only at one special composition.
- The logarithmic divergence of $S/T$ and the ~25 K hump appear in both parent-like clean films and in a superconducting film, so the critical signature is not tied to a single ground state.
- The coexistence of logarithmic $S/T$ with linear-in-temperature resistivity in the superconducting film suggests a common origin in magnetic quantum critical fluctuations.
- Disorder turns off the critical behavior, so sample cleanliness is an essential condition for observing the nickelate analogue of cuprate criticality.
- Short-range antiferromagnetic order below ~25 K, inferred from fourfold symmetry breaking in magnetoresistance, strengthens the case that antiferromagnetic spin correlations are involved in the pairing mechanism.
Reading between the lines
- If the quantum-critical interpretation survives further tests, thermopower becomes a practical bulk probe for mapping the putative critical region in nickelates, complementing resistivity and specific-heat measurements.
- A testable extension the paper does not spell out: controlled disorder, such as ion irradiation or thickness variation in a single film series, should smoothly convert divergent $S/T$ into flat $S/T$, giving a quantitative tuning curve for the proposed transition from band-dominated to critical-dominated transport.
- One can directly test whether the 25 K hump carries magnetic entropy by measuring the heat capacity or thermal expansion of the same clean films; a magnetic ordering feature there would independently corroborate the magnetoresistance inference.
- The same thermoelectric signature should appear in other clean infinite-layer nickelate compositions such as LaNiO$_2$ or PrNiO$_2$ if antiferromagnetic quantum criticality is generic to the family.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper reports Seebeck-coefficient measurements on infinite-layer nickelate films with different disorder levels. According to the abstract, a disordered NdNiO2 film shows a flat S/T, whereas cleaner films show a logarithmic divergence of S/T at low temperature plus a pronounced hump near 25 K; in-plane angular magnetoresistance below the hump shows fourfold symmetry breaking, which the authors interpret as short-range antiferromagnetic order. A clean superconducting Sm0.73Ca0.05Eu0.22NiO2 film is reported to show the same logarithmic S/T divergence coexisting with linear-in-temperature resistivity over the same range. The paper concludes that these observations demonstrate quantum criticality over a wide doping range in clean infinite-layer nickelates, similar to cuprates. The full text received is, however, unreadable mojibake, so the experimental details, fits, figures, and error bars cannot be independently checked.
Significance. If the central claim holds, it would be an important addition to the nickelate-superconductivity literature, linking thermoelectric response and magnetotransport to antiferromagnetic quantum criticality and strengthening the analogy to cuprates. The combination of S/T behavior and symmetry-breaking AMR in clean superconducting films is potentially significant. However, the claim depends on the interpretation that the logarithmic S/T and the 25 K hump are quantum-critical signatures, and the manuscript as received does not permit verification of the underlying data or exclusion of alternative mechanisms such as phonon drag, Kondo/impurity scattering, or band-structure effects. The significance is therefore conditional.
major comments (4)
- [Full text] The submitted full text is garbled mojibake (e.g., '����� �� ��� ...'), with no readable equations, figure captions, tables, methods, sample characterization, or error bars. I cannot verify the central experimental claims, the fit ranges, the measurement protocols, or the AMR data. A readable, machine-processable manuscript is a precondition for review.
- [Abstract] The key inference—that S/T ~ log T plus a 25 K hump indicates AFM quantum criticality—is not unique. Phonon drag produces a low-temperature hump; Kondo/impurity scattering can produce a logarithmic-like S/T over a finite window; and a Lifshitz or van Hove band feature can also build up with decreasing temperature. The abstract gives no fit range, no test against power-law alternatives, and no quantitative comparison of the hump amplitude with disorder level. Please add fits and diagnostic tests that discriminate quantum-critical from noncritical mechanisms, such as magnetic-field dependence, a doping/disorder series, or thermal-conductivity data.
- [Abstract] Fourfold symmetry breaking in the in-plane angular magnetoresistance is presented as evidence of short-range antiferromagnetic order. Fourfold symmetry breaking is compatible with, but not unique to, AFM order; nematicity, orbital/stripe order, or a structural distortion would also produce it. If there is additional evidence—for example, magnetic susceptibility anisotropy, neutron scattering, or a specific heat anomaly—it should be presented. Without that, the inference to AFM order is underdetermined.
- [Abstract] The claim of 'quantum criticality over a wide doping range' rests on two compositions (NdNiO2 and Sm0.73Ca0.05Eu0.22NiO2) and does not involve tuning through a quantum critical point. Coexistence of logarithmic S/T and linear resistivity in one clean superconducting film is suggestive but does not by itself establish a QCP. Please specify what temperature range is used for the logarithmic fit, whether the same range applies to the linear resistivity, and what scaling forms or other QC-specific predictions are tested.
minor comments (3)
- [Abstract] The term 'clean' is not quantified. Please state the residual-resistivity ratio, film thickness, strain state, and any disorder metric used to distinguish 'disordered' from 'clean' samples.
- [Abstract] The sample formula Sm0.73Ca0.05Eu0.22NiO2 should be explicitly tied to the nominal oxidation state and to the superconducting transition temperature, and the temperature range of the S/T divergence should be given in the text, not only implied by a figure.
- [General] Please ensure all symbols, especially S/T and the 'hump' temperature, are defined and that units are specified. Also add comparisons with existing Seebeck data on nickelates and cuprates to contextualize the claimed similarity.
Circularity Check
Moderate definitional circularity: the S/T log divergence is labeled 'quantum-critical-dominated transport' and then cited as evidence for quantum criticality.
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self definitional
[Abstract, first paragraph]
"The disordered NdNiO₂ film exhibits a flat S/T curve, whereas cleaner samples display a logarithmic divergence with decreasing temperature, followed by a pronounced ``hump'' near 25 K. These distinct behaviors reveal a disorder-driven transition from band-structure-dominated transport to quantum-critical-dominated transport."
The paper assigns the labels 'band-structure-dominated' and 'quantum-critical-dominated' to the observed S/T shapes themselves: flat S/T is called band-structure-dominated, log-divergent S/T is called quantum-critical-dominated. The conclusion that cleaner samples reveal a transition to quantum-critical-dominated transport is therefore a restatement of the observed S/T morphology under an interpretive label, not an independent test. No separate observable—such as a continuous tuning parameter through a quantum critical point, divergent correlation length, or an independent thermodynamic anomaly—is used to establish the quantum critical state; the diagnostic signature is effectively the phenomenon being claimed.
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self definitional
[Abstract, final paragraph]
"Furthermore, the logarithmic divergence in S/T is also observed in a clean superconducting Sm₀.₇₃Ca₀.₀₅Eu₀.₂₂NiO₂ film, where it coexists with linear-in-temperature resistivity over the same temperature range. These findings demonstrate the existence of quantum criticality over a wide doping range in clean infinite-layer nickelate films, similar to cuprates, which highlights the central role of antiferromagnetic spin correlations in their superconducting pairing mechanisms."
The 'findings' cited are precisely the log S/T divergence and the linear-in-temperature resistivity—the two transport signatures that the paper's interpretive framework treats as the thermoelectric fingerprint of quantum criticality. Demonstrating quantum criticality by observing those signatures applies the framework's diagnostic criteria rather than independently testing the framework. The additional fourfold AMR anisotropy could in principle supply independent evidence, but the identification of that anisotropy with short-range antiferromagnetic order is itself an interpretive step and does not by itself supply a control parameter that moves the system through a quantum critical point.
full rationale
The paper is an experimental transport study, not a derivation with equations or fitted parameters that are renamed as predictions. There is no equation-level identity between inputs and outputs, and no fitted parameter is presented as an independent prediction. The central circularity concern is definitional/interpretive: the observed log-divergent S/T (and linear rho) is classified as 'quantum-critical-dominated transport,' and then the same observation is said to 'demonstrate the existence of quantum criticality.' This is a standard phenomenological arc, but it does reduce, at least in part, to equating the signature with the phenomenon. The paper's additional content—the disorder comparison, the hump, and the AMR fourfold symmetry breaking—is non-circular observational evidence, but it does not fully break the tautology because the interpretation of those features as quantum critical / short-range AFM order is itself part of the same classification scheme. Because the central claim leans on its own diagnostic labeling rather than on an independent critical-point determination, a moderate circularity score of 4 is appropriate. Note: the supplied full text is heavily corrupted, so this analysis is based primarily on the readable abstract and visible in-scope text.
Assumptions & free parameters
free parameters (3)
- Film disorder level
- Sample stoichiometry Sm0.73Ca0.05Eu0.22NiO2 =
Sm:Ca:Eu = 0.73:0.05:0.22
- Temperature range for the S/T logarithmic fit
assumptions (3)
- domain assumption A logarithmic divergence of S/T at low temperature is a signature of quantum critical fluctuations
- domain assumption Linear-in-temperature resistivity in the same temperature range indicates non-Fermi-liquid quantum critical scattering
- domain assumption Fourfold symmetry breaking in in-plane angular magnetoresistance implies short-range antiferromagnetic order
Cite this review
Pith. "Pith review of Thermoelectricity evidence for quantum criticality in clean infinite-layer nickelate films." pith.science (2026). https://pith.science/paper/UJQ2EI46
@misc{pith2026250812974,
author = {Pith},
title = {Pith review of: Thermoelectricity evidence for quantum criticality in clean infinite-layer nickelate films},
year = {2026},
howpublished = {\url{https://pith.science/paper/UJQ2EI46}},
note = {Machine review of arXiv:2508.12974}
}
abstract
We investigate the Seebeck coefficient ($S$) in infinite-layer nickelate films with different disorder levels. The disordered NdNiO$_{2}$ film exhibits a flat $S/T$ curve, whereas cleaner samples display a logarithmic divergence with decreasing temperature, followed by a pronounced ``hump'' near 25 K. These distinct behaviors reveal a disorder-driven transition from band-structure-dominated transport to quantum-critical-dominated transport. Below the ``hump'' temperature, four-fold symmetry breaking is observed in the in-plane angular magnetoresistance, indicating the presence of short-range antiferromagnetic order in parent infinite-layer nickelate films. Furthermore, the logarithmic divergence in $S/T$ is also observed in a clean superconducting Sm$_{0.73}$Ca$_{0.05}$Eu$_{0.22}$NiO$_{2}$ film, where it coexists with linear-in-temperature resistivity over the same temperature range. These findings demonstrate the existence of quantum criticality over a wide doping range in clean infinite-layer nickelate films, similar to cuprates, which highlights the central role of antiferromagnetic spin correlations in their superconducting pairing mechanisms.
Forward citations
Cited by 1 Pith paper
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A Disconnected Superconducting Regime at the Parent Limit of Infinite-Layer Nickelates
Stoichiometric uncapped PrNiO2 shows zero resistance and diamagnetism, defining a narrow superconducting regime at the parent limit that is separated from the known doped dome.
Reviewed August 5, 2026 · model on record in the stance chip above.
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