REVIEW 3 major objections 2 minor 3 references
Reply to the Comment by Tikhonov and Khrapai on "Long-range crossed Andreev reflection in a topological insulator nanowire proximitized by a superconductor"
T0 review · 3 major / 2 minor · reviewed 2026-08-05 · deepseek-v4-flash
Pith's one-line read The comment against long-range crossed Andreev reflection does not refute it: its own argument relies on a large CAR contribution.
desk verdict A rebuttal that scores a fair point on the CAR/ECT framing but overreaches on the central inference: T_he≈T_ee does not establish 'large long-range CAR'. 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 identity is Eq. (1) of the reply (Eq. (5) of the comment): G12/G0 = (1/e) ∂/∂V2 ∫_{0}^{eV2} [T_he^12(E,V1,V2) - T_ee^12(E,V1,V2)] dE. It expresses the normalized nonlocal conductance as the bias derivative of the energy integral of the difference between crossed Andreev reflection and elastic co-tunneling transmissions. This identity carries the argument because it shows that any nonlinearity or bias dependence in the data must enter through the voltage- and energy-dependence of T_he^12 and T_ee^12, so a Taylor expansion cannot remove the CAR/ECT competition; it only renames it.
What would settle it
Take the nonlocal conductance data of the original paper and fit it with the comment's Taylor-expansion model while forcing T_he^12 = 0 (no CAR) and leaving self-gating parameters free. If a good fit is found, the reply's assertion that the comment relies on a large CAR is falsified.
Extended reading notes
Core claim
The authors' central claim is that a comment aimed at refuting their findings actually presupposes and supports them. The comment explains the measured nonlocal conductance by invoking a finite CAR transmission T_he^12 of similar magnitude to the ECT transmission T_ee^12, which is exactly the sizable long-range CAR contribution reported originally; and it emphasizes the complicated dependence of CAR and ECT on gates and biases, which was the original conclusion about local and global effects. The reply further holds that a Taylor expansion of the conductance into symmetry-allowed nonlinear terms, with names such as 'self-gating', does not contradict bias-controlled manipulation of CAR and EC
Load-bearing premise
The reply assumes that a finite CAR transmission comparable to ECT in the comment's model counts as endorsing a sizable long-range CAR, but the comment might treat CAR only as a generic background process while disputing its dominance or long-range character.
Editorial extensions
If this is right
- The comment's own success in describing the data confirms that CAR is sizable and comparable to ECT, as originally reported.
- Bias-independent transmission models cannot explain the observed data, so voltage- and energy-dependent T_he^12 and T_ee^12 are necessary ingredients.
- The bias-combination controllability of the CAR/ECT competition follows directly from Eq. (5), without invoking nonlinear self-gating terms.
- The strong sensitivity of nonlocal conductance to gate and bias configurations is a central physical message, not a fine-tuned artifact.
- Disputes over wording such as 'dominant CAR' do not alter the quantitative content of the conductance formula.
Reading between the lines
- If the comment's Taylor expansion is taken as the full explanation, the same data might be reproduced with a negligible CAR term; an explicit fit with T_he^12 = 0 would test whether the comment truly relies on CAR.
- A direct length-dependence measurement of the nonlocal signal would settle whether the CAR contribution is genuinely long-range, since the reply's argument establishes presence of CAR in the transmission sum but not its spatial profile.
- The resolution of this exchange suggests that in mesoscopic superconductor experiments, reporting differential conductance formulas as the difference of competing transmission channels could prevent similar semantic disputes.
- One could use Eq. (5) to extract energy-resolved T_he^12 and T_ee^12 from multi-bias measurements, turning the debate into a quantitative spectroscopy question.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This Reply by Feng et al. defends their Nature Physics paper (Ref. 1) against the Comment by Tikhonov and Khrapai (Ref. 2). The Reply makes two central claims: (i) the Comment's model uses a finite crossed-Andreev-reflection transmission T_he^12 with T_he^12 ≈ T_ee^12, which the Reply interprets as evidence that the Comment relies on a large, long-range CAR; and (ii) the Comment's discussion of nonlinear transport and self-gating actually supports the Reply's second conclusion about the complex interplay between CAR and elastic co-tunneling. The Reply also rejects the Comment's criticism of the authors' citation of Ref. 3 and characterizes the Comment's 'fine-tuning' remark as consistent with the paper's message.
Significance. If the Reply's interpretation were correct, it would show that the Comment does not undermine the original paper's conclusions. However, the Reply's central inference is logically insufficient: equality of two transmission coefficients does not establish their absolute magnitude or spatial range. The Reply also conflates total-current bias dependence with differential conductance, and its use of the Comment's Eq. (5) does not resolve the quantitative question of whether CAR is sizable and long-ranged. The Reply provides no new data or calculations and does not quote parameter values from the Comment. The paper does contain one useful clarification—that the nonlinear Taylor expansion can be re-expressed in terms of energy-dependent T_he and T_ee—but this is not enough to support the Reply's headline claim.
major comments (3)
- [Paragraph 2 (T_he^12 ≈ T_ee^12)] The abstract and first paragraph assert that the Comment 'explicitly relies on a large CAR effect' and that T_he^12 ≈ T_ee^12 'implies a large CAR contribution.' This inference is not demonstrated. T_he^12 ≈ T_ee^12 is a relative statement: both coefficients could be equally small, and equality alone contains no information about the spatial decay length, which is essential to the original claim of a 'surprisingly long distance' CAR. To make this claim load-bearing, the Reply must quote the Comment's own statements or numerical model parameters showing that T_he^12 is large in absolute terms and extends over the relevant length. Without that, the Reply's first and central point is an assertion, not a refutation of the Comment.
- [Paragraph 3 (Ref. 3)] The Reply states that the figures in Ref. 3 'clearly show a dependence of the magnitude of current on bias voltage combination, i.e., the differential conductance.' This is a category error: a dependence of total current on bias voltages is not the same as differential conductance, which is a derivative of that current. The Comment's criticism was about what Ref. 3 primarily discusses, not whether the underlying I-V data have structure. This rebuttal therefore does not answer the Comment's point.
- [Eq. (1) and the self-gating argument] The Reply uses the Comment's Eq. (5) to argue that one can 'directly' discuss CAR/ECT competition. But Eq. (5) expresses nonlocal conductance as the derivative of an integral of T_he - T_ee. If T_he ≈ T_ee, the difference inside the integral can be small even when T_he is large, and the observed conductance can be dominated by the bias dependence of the transmissions (the Comment's 'self-gating'). The Reply does not show how the data distinguish this possibility from a large absolute CAR. Thus the Reply's defense of the 'complex interplay' conclusion does not by itself establish the 'sizable long-range CAR' claim; it actually illustrates why the Comment's concern is substantive rather than merely semantic.
minor comments (2)
- [Paragraph 2] Typo: 'Tikohnov' should be 'Tikhonov'.
- [Throughout] The Reply does not quote or cite any specific passage from the Comment beyond Eq. (5), which makes it difficult for the reader to verify the Reply's characterization of the Comment's assumptions. Adding precise quotations or equation numbers for the Comment's claims would strengthen the Reply.
Circularity Check
No significant circularity: the reply's inference is interpretive, not a self-referential derivation.
full rationale
The reply contains no derivation of a new result from fitted inputs and does not rename a fitted parameter as a prediction. Its central move is to argue that the Comment's own use of a finite T_he^12 with T_he^12 ≈ T_ee^12 supports the original claim of a sizable CAR. That is an interpretive argument about the Comment's model, not a reduction of the reply's conclusion to its own input. The reply reproduces the Comment's Eq. (5) as Eq. (1) to discuss CAR/ECT competition; because this equation is supplied by the Comment rather than derived from the reply's assumptions, using it does not make the conclusion an input. Self-citations to Ref. [1] simply restate the original conclusions being defended and are not load-bearing evidence imported to force the reply's conclusion. No step in the reply equates a prediction with an input by construction, and no self-citation chain substitutes for independent argument. The weakness of the inference from T_he^12 ≈ T_ee^12 to 'large long-range CAR' is a matter of evidential support, not circularity.
Assumptions & free parameters
assumptions (3)
- domain assumption The comment's Eq. (5) (reproduced as Eq. (1) in the reply) is a valid and complete model for the nonlocal conductance in the experiment.
- domain assumption A finite T_he^12 comparable to T_ee^12 constitutes 'sizable long-range CAR'.
- domain assumption Bias dependence of the measured nonlocal conductance implies bias-dependent transmission probabilities and invalidates the comment's bias-independent model.
Cite this review
Pith. "Pith review of Reply to the Comment by Tikhonov and Khrapai on "Long-range crossed Andreev reflection in a topological insulator nanowire proximitized by a superconductor"." pith.science (2026). https://pith.science/paper/OKVFOLHK
@misc{pith2026250905153,
author = {Pith},
title = {Pith review of: Reply to the Comment by Tikhonov and Khrapai on "Long-range crossed Andreev reflection in a topological insulator nanowire proximitized by a superconductor"},
year = {2026},
howpublished = {\url{https://pith.science/paper/OKVFOLHK}},
note = {Machine review of arXiv:2509.05153}
}
read the original abstract
The comment (arXiv:2505.23490) fails to identify any scientific errors and its central arguments actually support the main conclusions of our publication [Nat. Phys. 21, 708 (2025)]. Firstly, the whole argument of the comment to try to explain our data explicitly relies on the existence of a large crossed Andreev reflection (CAR) effect. The presence of a sizable CAR transmission probability over a surprisingly long distance is the first conclusion of our publication. Secondly, the comment discusses the complex interplay of CAR and elastic co-tunneling, especially in the presence of local effects. This complex interplay is precisely the second conclusion of our publication. In essence, the comment amounts to merely pointing out that there is a broader sense in the notion of "dominant CAR" when nonlinear effects become relevant.
Reference graph
Works this paper leans on
-
[1]
J. Feng, H. F. Legg, M. Bagchi, D. Loss, J. Klinovaja, and Y . Ando, Nature Physics21, 708 (2025)
work page 2025
-
[2]
E. S. Tikhonov and V . S. Khrapai, (2025), arXiv:2505.23490 [cond-mat.mes-hall]
work page Pith review arXiv 2025
- [3]
Reviewed August 5, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.