Comment on arXiv:1807.08572: a plausible explanation of the giant diamagnetism found in Au-Ag nanostructures

Navinder Singh

arxiv: 1906.08128 · v1 · pith:KNKWROQGnew · submitted 2019-06-19 · ❄️ cond-mat.supr-con · cond-mat.str-el

Comment on arXiv:1807.08572: a plausible explanation of the giant diamagnetism found in Au-Ag nanostructures

Navinder Singh This is my paper

Pith reviewed 2026-05-25 19:58 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con cond-mat.str-el

keywords giant diamagnetismquantum confinementnanoparticlesLangevin diamagnetismAu-Ag nanostructureselectronic energy gapsscattering suppression

0 comments

The pith

Giant diamagnetism in Au-Ag nanostructures may arise from quantum confinement creating energy gaps that suppress scattering and enhance Langevin diamagnetism.

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

This comment proposes an explanation for the giant diamagnetism reported alongside vanishing resistance in Au-Ag nanostructures. The author argues that quantum confinement in the nanoparticles opens gaps in the electronic energy spectrum. These gaps reduce electron scattering enough to produce a much larger Langevin diamagnetism than in bulk metals. The suggestion addresses the diamagnetism left unexplained by an earlier comment that focused on the resistance data and favored a percolation interpretation over superconductivity.

Core claim

The giant diamagnetism found in the nanostructures could be due to a gapped electronic energy spectrum of nanoparticles arising from quantum confinement effects; this suppresses the electronic scattering mechanism and leads to a very high value of Langevin diamagnetism.

What carries the argument

Gapped electronic energy spectrum due to quantum confinement in nanoparticles, which suppresses scattering to enhance Langevin diamagnetism.

If this is right

The diamagnetism would be a size-dependent quantum effect rather than evidence of superconductivity.
The magnetic response would appear only when particle dimensions are small enough for confinement gaps to matter.
No percolating superconducting transition is required to explain the combined resistance and magnetism data.

Where Pith is reading between the lines

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

The same confinement mechanism could be tested in other metallic nanoparticle compositions by changing size while holding composition fixed.
Quantitative modeling of the gap versus scattering rate would be needed to check whether the magnitude matches experiment.
If the gaps are real, optical or tunneling spectroscopy on the same samples should reveal the gap energy scale.

Load-bearing premise

Quantum confinement in these specific Au-Ag nanoparticles produces energy gaps large enough to suppress scattering sufficiently to match the reported giant diamagnetism magnitude.

What would settle it

A calculation of the confinement gap size for the reported nanoparticle dimensions, or a direct measurement of the gap, showing it is too small to suppress scattering enough to reach the observed diamagnetism strength.

Figures

Figures reproduced from arXiv: 1906.08128 by Navinder Singh.

**Figure 1.** Figure 1: Discrete electronic states on the surface of a nanoparticle. Let R be the radius of a nanoparticle. Imposing periodic boundry condition on a closed orbit of a surface elecron along the peripheri of the nanoparticle (figure 1), we get quatized wavevectors n 2π L . The nth energy level is given by En = n 2h¯ 2 2mR2 , and the energy gap by ∆En = En+1 − En = h¯ 2 2mR2 (2n + 1). (2) When this gap becomes bigge… view at source ↗

read the original abstract

In a recent comment (arXiv:1906.05742) on the preprint (arXiv:1807.08572) entitled "Coexistence of Diamagnetism and Vanishingly Small Electrical Resistance at Ambient Temperature and Pressure in Nanostructures", it is pointed out that the reduction of the four-probe resistance ($R_{4P}$) to zero value is accompanied by a rise in the two probe resistance ($R_{2P}$) in the same temperature range. This curious correlation between $R_{4P}$ and $R_{2P}$ is said to be pointing towards a non-superconducting "conductance percolation" transition (rather than "percolating superconducting transition" as proposed in the revised version of arxiv:1807.08572). The explanation offered in preprint arXiv:1906.05742 is quite reasonable, but the author leaves open the question of giant diamagnetism. In this short comment I suggest a plausible cause of the giant diamagnetism found in nanostructures. It could be due to gapped electronic energy spectrum of nanoparticles which is due to quantum confinement effects, and that suppresses the electronic scattering mechanism leading to a very high value of Langevin diamagnetism.

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.

Desk Editor's Note private letter to a colleague

This comment floats quantum confinement as a cause for the reported giant diamagnetism but supplies no gap estimates, no susceptibility calculation, and an incorrect link to scattering rates.

read the letter

The central suggestion is that quantum confinement in the Au-Ag nanoparticles opens an energy gap, reduces scattering, and thereby produces a very large Langevin diamagnetism. That is the whole new claim; everything else is context from the earlier comments on the resistance data. The paper does at least isolate the diamagnetism as the remaining unexplained feature once the zero-resistance signal is reinterpreted as percolation rather than superconductivity. It also correctly notes that the original work left this point open. Beyond that, the text contains no derivation, no numerical estimate of confinement energy for the reported particle sizes, and no comparison against the measured susceptibility values. The proposed mechanism itself does not hold: Langevin diamagnetism is an equilibrium orbital response and does not depend on scattering time. The paper therefore offers no working connection between the gap and the observed effect. There are no equations, no figures, and the references are only to the two preprints being discussed. This is a short interpretive note rather than a result. It might interest people already following the nanostructure claims, but it does not contain enough substance or grounding to justify referee time. I would not bring it to a reading group or cite it. Recommendation is desk reject.

Referee Report

2 major / 0 minor

Summary. The manuscript is a brief comment on arXiv:1807.08572 proposing that the reported giant diamagnetism in Au-Ag nanostructures arises from quantum-confinement-induced gaps in the nanoparticle electronic spectrum; these gaps are said to suppress scattering and thereby produce a very large Langevin diamagnetism.

Significance. The suggestion offers a non-superconducting alternative for the diamagnetism but supplies neither a derivation relating gap size to susceptibility nor any numerical estimate for the nanoparticles in question, so the result would not alter understanding of the original data even if the mechanism were valid.

major comments (2)

[main text] Main text, paragraph 2: the assertion that a gapped spectrum 'suppresses the electronic scattering mechanism leading to a very high value of Langevin diamagnetism' is incorrect on its face; Langevin diamagnetism is an equilibrium orbital response whose magnitude is set by the atomic or band diamagnetic susceptibility and is independent of scattering rate.
[main text] Main text: no estimate is given for the confinement energy ħ²/2mR² at the nanoparticle radii of arXiv:1807.08572, nor is any susceptibility calculation performed to show that the proposed gaps would reproduce the reported diamagnetic values; the claim therefore remains a qualitative conjecture without quantitative support.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and comments on our brief comment manuscript. We respond point by point to the major comments below.

read point-by-point responses

Referee: Main text, paragraph 2: the assertion that a gapped spectrum 'suppresses the electronic scattering mechanism leading to a very high value of Langevin diamagnetism' is incorrect on its face; Langevin diamagnetism is an equilibrium orbital response whose magnitude is set by the atomic or band diamagnetic susceptibility and is independent of scattering rate.

Authors: We agree that the referee's point is correct and that the original phrasing was imprecise. Langevin diamagnetism is indeed an equilibrium orbital response independent of scattering. The manuscript intended to propose that quantum confinement gaps modify the electronic structure to enhance diamagnetic response, but the link to scattering suppression is not accurate. We will revise the text to remove the incorrect statement. revision: yes
Referee: Main text: no estimate is given for the confinement energy ħ²/2mR² at the nanoparticle radii of arXiv:1807.08572, nor is any susceptibility calculation performed to show that the proposed gaps would reproduce the reported diamagnetic values; the claim therefore remains a qualitative conjecture without quantitative support.

Authors: The referee correctly notes that the suggestion is qualitative. As this is a short comment, a full quantitative derivation relating gap size to susceptibility was outside its intended scope. We will add a rough estimate of the confinement energy ħ²/2mR² using the nanoparticle radii from the original work to provide some quantitative context, though a complete susceptibility calculation remains beyond the scope of this note. revision: partial

Circularity Check

0 steps flagged

No circularity; qualitative hypothesis with no equations, fits, or self-referential derivations.

full rationale

The manuscript offers a one-paragraph suggestion that quantum confinement in nanoparticles produces a gapped spectrum which 'suppresses the electronic scattering mechanism leading to a very high value of Langevin diamagnetism.' No equations appear, no parameters are fitted or renamed as predictions, no self-citations are invoked as load-bearing uniqueness theorems, and no ansatz is smuggled in. The claim is therefore not equivalent to its inputs by construction; it remains an unquantified conjecture whose validity can be assessed externally against measured gap sizes and susceptibility values.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The claim rests entirely on an unquantified domain assumption about the strength of quantum confinement effects; no free parameters or new entities are introduced because no model is built.

axioms (1)

domain assumption Quantum confinement in the Au-Ag nanoparticles creates a gapped spectrum that suppresses scattering enough to produce giant Langevin diamagnetism.
Invoked directly in the abstract as the cause of the observed diamagnetism.

pith-pipeline@v0.9.0 · 5756 in / 1091 out tokens · 24437 ms · 2026-05-25T19:58:10.300890+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

3 extracted references · 3 canonical work pages

[1]

Hernando, A

A. Hernando, A. Ayuela, P . Crespo, and P . M. Echenique, New J. Phys. 16, 073043 (2014)

work page 2014
[2]

Pankaj Bhalla and Navinder Singh, Eur. Phys. J. B 89, 40 (2016)

work page 2016
[3]

Navinder Singh, Electronic T ransport Theo- ries: From Weakly to Strongly Correlated Ma- terials, CRC Press (2016). 5

work page 2016

[1] [1]

Hernando, A

A. Hernando, A. Ayuela, P . Crespo, and P . M. Echenique, New J. Phys. 16, 073043 (2014)

work page 2014

[2] [2]

Pankaj Bhalla and Navinder Singh, Eur. Phys. J. B 89, 40 (2016)

work page 2016

[3] [3]

Navinder Singh, Electronic T ransport Theo- ries: From Weakly to Strongly Correlated Ma- terials, CRC Press (2016). 5

work page 2016