{"id":"cf4ac11b-7a07-4e3d-958c-bcd1113ed3c3","arxiv_id":"2411.14648","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"A SrIrO3 buffer stabilizes metallic, ferromagnetic SrRuO3 down to one monolayer and produces Hall humps with a constant AHE sign, which the authors interpret as intrinsic skyrmion signatures.","lead":"Using a strontium iridate buffer layer, the authors kept strontium ruthenate films metallic and magnetic down to a single atomic layer, and they measured a Hall-effect hump whose sign behavior they argue can only come from skyrmion-like spin textures. This matters because the same hump in other ruthenate films has been explained as a two-layer artifact, and the new result would support atomic-scale magnetic skyrmions for future spintronics.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Persistent negative AHE sign cannot by itself exclude two-channel THE, because an opposite-sign channel with smaller magnitude can still produce a hump while the total loop remains negative; the central skyrmion inference needs a two-component fit or layer-resolved control.","rationale":"The paper's central claim is that a persistently negative AHE sign, observed together with hump-like Hall features, excludes the two-channel explanation and therefore provides evidence for skyrmions. The reader identified the lack of a bare SrIrO3 control and the ARPES/transport stack mismatch as the weakest assumption. I agree those are serious attribution gaps, but there is a more fundamental logical issue: even if all measured Hall signal comes from SrRuO3, a superposition of two opposite-sign anomalous Hall channels can produce a hump while the net Hall loop remains negative whenever the negative channel is the larger contributor. The sign of a sum does not determine the signs of the summands. Consequently, the paper's exclusion argument is not valid as written. This is not a disagreement with external consensus; it is an internal inference gap in the argument connecting the data to the skyrmion conclusion. The gap is addressable: a two-component fit of the Hall loops, or layer-resolved Hall measurements, would settle whether the hump can be reproduced by opposite-sign channels. Because the required check is concrete and feasible, I recommend a conditional verdict rather than outright rejection: the manuscript should be revised to include the control experiment and/or demonstrate that a two-channel model cannot fit the measured loops. No ad hominem is intended; the experimental observations may be sound, but the central interpretive claim is not yet established.","tokens_in":9584,"tokens_out":5546,"duration_ms":63450,"concrete_test":"Take the symmetrized R_xy(H) loops for the 20+6 and 20+8 heterostructures and fit them to a two-component anomalous Hall model, e.g. R_AHE(H) = A1 M1(H-Hc1) + A2 M2(H-Hc2), with M1 and M2 taken from independent magnetization loops of the stack and of a bare 20 u.c. SrIrO3 control film, allowing A1 and A2 to have opposite signs. If the model reproduces the measured hump while the fitted total AHE remains negative across the full field range, then the persistent negative AHE sign does not exclude the two-channel explanation; if no such fit is possible and the control film is inert, the central skyrmion inference is supported.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The load-bearing step is the claim in the Results and Discussion sections that 'the AHE sign remains negative over a wide thickness range, where THE is still observed. This observation excludes the two-channel explanation of THE.' This inference is logically incomplete. In the two-channel model, the measured Hall signal is a sum R_AHE(H) = R1(H) + R2(H), where R1 and R2 have opposite signs and different coercive fields. A hump appears when the two channels switch at different fields, but the total can remain negative throughout the field sweep whenever the negative channel has larger magnitude than the positive channel at every field. Thus, a persistently negative overall AHE loop does not rule out a hidden positive channel; it only rules out two channels whose positive contribution is large enough to flip the total sign. The paper provides no bare 20 u.c. SrIrO3 control and no decomposition of the Hall loops into independent magnetic components; the ARPES check was also performed on [SrIrO3]5/[SrRuO3]n rather than the 20 u.c.-buffered transport stacks, so the electronic-structure-to-transport link rests on an unstated transfer assumption. Unless the two-channel model is explicitly fitted and rejected, the central conclusion that the hump features are intrinsic skyrmion signatures is not established.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports on [SrIrO3]20/[SrRuO3]n heterostructures grown on SrTiO3, with n = 1 to 10 monolayers. The authors claim that interfacing SrRuO3 with a 20 u.c. SrIrO3 buffer maintains metallicity and ferromagnetism down to the monolayer limit, as evidenced by transport (rho-T kinks) and SQUID magnetization. In-situ ARPES on [SrIrO3]5/[SrRuO3]n stacks is used to argue that the topological band structure is preserved at ultrathin thicknesses. Hall measurements show a negative anomalous Hall effect that persists over a wide thickness and temperature range, while hump-like features (called 'topological Hall effect') are observed in the 20+6 and 20+8 samples. The central claim is that the persistent negative AHE sign excludes a two-channel (opposite-sign AHE superposition) explanation of the hump and therefore provides evidence for skyrmions in ultrathin SrRuO3.","tokens_in":9798,"tokens_out":6182,"duration_ms":57927,"significance":"The paper addresses an important controversy in oxide spintronics: whether hump-like Hall features in SrRuO3 are intrinsic topological Hall signals or artifacts from superimposed anomalous Hall contributions. It provides systematic transport and ARPES data for SrRuO3 down to the monolayer limit on a SrIrO3 buffer, demonstrating metallicity, ferromagnetism, and a preserved band dispersion. The experimental dataset is a strength, particularly the thickness series and the use of in-situ ARPES. If the central exclusion argument were quantitatively established, this would be a valuable contribution. However, the logical gap in excluding the two-channel model and the absence of necessary control experiments mean that the skyrmion claim is not yet established.","major_comments":[{"comment":"The inference that a persistent negative AHE sign excludes a two-channel explanation is logically incomplete. In the two-channel model, the total Hall signal is R_AHE(H) = R1(H) + R2(H), where R1 and R2 have opposite signs and different coercive fields. A hump can appear when the two channels switch at different fields, even if the total remains negative at every field, provided the negative channel dominates in magnitude. The manuscript does not perform a two-component fit of the Hall loops, nor does it provide a layer-resolved control that isolates each channel. Therefore the statement in the Results that 'The persistent negative AHE sign ... rules out the possibility of opposite AHE contributions' is not substantiated. Please provide a quantitative two-component analysis or an explicit demonstration that no positive channel of any magnitude is present.","section":"Results, Fig. 4 and Discussion"},{"comment":"No bare 20 u.c. SrIrO3 control is reported. All Hall measurements are performed on full 20+n stacks, and the 'anomalous Hall signal' is operationally defined by symmetrisation and subtraction of the normal Hall effect. Without a measurement of the 20 u.c. SrIrO3 film alone, the possible anomalous or topological Hall contribution from the buffer and the interface cannot be excluded. This omission is load-bearing because the claim that the AHE sign is negative for SrRuO3 requires that the measured signal be attributable to SrRuO3 rather than to the SrIrO3 buffer or interface.","section":"Methods and Results, Hall measurements"},{"comment":"The ARPES data in Fig. 2 were obtained on [SrIrO3]5/[SrRuO3]n heterostructures, whereas the transport data in Figs. 3 and 4 are on [SrIrO3]20/[SrRuO3]n stacks. The manuscript does not justify this buffer-thickness difference or state that the electronic structure is unaffected by the thicker buffer. The connection between the measured band structure and the transport-derived topological Hall effect therefore rests on an unstated transfer assumption. Please either perform ARPES on the 20 u.c.-buffered stacks or provide a reasoned justification for why the 5 u.c. result is representative.","section":"Fig. 2 and Fig. 3, ARPES versus transport stacks"},{"comment":"The manuscript refers to a 'THE signal' in Fig. 4(b) but does not describe how the topological Hall contribution is extracted from the AHE background. No subtraction formula, fitting procedure, or criterion is given. Without a clear definition of how the hump is isolated, the reader cannot distinguish a genuine topological Hall signal from a non-linear background or from the tail of the ordinary anomalous Hall loop. Please specify the extraction method and show the background used.","section":"Fig. 4(b), THE extraction"},{"comment":"The transport data are presented as single representative curves without error bars or sample-to-sample statistics. The central claim is that the negative AHE sign is robust over a wide thickness and temperature range. Reporting reproducibility information, such as the number of samples per thickness, the spread of the sign and magnitude of the AHE, and the field position of the hump, is necessary to substantiate this robustness claim.","section":"Figs. 3 and 4, reproducibility"}],"minor_comments":[{"comment":"The text states 'Fig. 2(a) shows the temperature dependent anomalous Hall signal,' but Fig. 2 contains the ARPES data; the temperature-dependent AHE is shown in Fig. 3(a). The figure citation should be corrected.","section":"Results, figure citations"},{"comment":"In the first Results paragraph, the text says 'The magnetic measurement of the hysteresis loop in Fig. 1(c) and temperature dependent magnetization in Fig. 1(d)', but the Fig. 1 caption indicates that (b) is the hysteresis loop, (c) is the resistivity, and (d) is the magnetization. The citations should be updated to match the figure panels.","section":"Results, figure citations"},{"comment":"Figure S2 is referenced for two different purposes: once for a single SrIrO3 ARPES map and later for the determination of the Curie temperature. Please renumber the supplementary figures so that each figure has a unique citation.","section":"Supplementary figures"},{"comment":"The text states that Hall measurements were performed for SrRuO3 thicknesses of 1, 2, 3, 4, 6, 8, and 10 u.c., while the Fig. 3 caption lists n = 1, 2, 3, 5, 6, 8, and 10. The inconsistency between 4 and 5 u.c. should be resolved and the measured thicknesses stated unambiguously.","section":"Figs. 3 and 4, thickness lists"},{"comment":"The title claims 'Manipulating ... Real-Space Topological States,' but the manuscript presents no real-space imaging; real-space skyrmions are inferred indirectly from transport. Please adjust the title or state explicitly in the text that the real-space evidence is indirect.","section":"Title and Abstract"},{"comment":"The Methods section contains the phrase 'The presented data presented were acquired,' which duplicates the word 'presented.' This should be corrected.","section":"Methods, ARPES sentence"}],"recommendation":"major_revision","confidential_remarks":"The paper addresses a high-profile controversy and the experimental work appears to be carefully done in terms of growth and characterization. However, the central inference against the two-channel AHE explanation needs quantitative support: either a two-channel fit of the Hall loops or a control that isolates the SrRuO3 contribution. The missing bare SrIrO3 control and the ARPES/transport stack mismatch are also essential to fix. If the authors can provide such evidence, the paper could be publishable; without it, the skyrmion claim is not established."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The paper has genuine new results: AHE in mono- and bi-layer SrRuO3, metallicity down to the monolayer limit, and preserved band structure by ARPES. Those are worth a careful look. The persistent negative AHE sign across a wide thickness range, with hump-like Hall features, is also a new experimental observation that extends the SrIrO3-buffer approach to a regime where sign flips had previously been seen.\n\nWhat it does not do is establish the central claim that the humps are intrinsic skyrmion signatures. The exclusion logic is the soft spot. The paper argues that a persistent negative AHE sign rules out the superposition of opposite-sign AHE channels, but that is not right. In a two-channel model with opposite signs and different coercive fields, a hump can appear whenever the two channels switch at different fields, and the total loop can remain negative the whole time if the negative channel dominates in magnitude. So the observation excludes only the special case where the positive channel is large enough to flip the sign. To make the argument stick, you need either a quantitative two-component fit of the Hall loops or a layer-resolved control that kills the hidden-channel alternative. Neither is here.\n\nThe paper also has a few more addressable gaps. There is no bare 20 u.c. SrIrO3 control, so the buffer's own AHE/THE contribution is uncharacterized. The ARPES was done on [SrIrO3]5/[SrRuO3]n stacks while the transport uses [SrIrO3]20, so the band-structure-to-transport link rests on an unstated transfer assumption. The \"THE signal\" in Fig. 4(b) has no described extraction method, and there are no error bars or sample repeats. The text also gives a slightly confusing account of the 20+10 sample's AHE temperature dependence. None of these is fatal; they are fixable with more measurements and clearer reporting.\n\nWho is this for? People working on SrRuO3 magnetotransport and oxide heterostructures will want to know these data. The paper deserves a serious referee, but the referee should insist on the two-channel fit and the SrIrO3 control before the skyrmion conclusion can be taken seriously. I would not cite the skyrmion claim as-is, but I would cite the metallization and monolayer AHE results.","headline":"Real new ultrathin SrRuO3 data, but the central skyrmion claim rests on an exclusion argument that does not actually exclude the two-channel model.","tokens_in":10400,"tokens_out":1735,"would_cite":true,"duration_ms":19209,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Hump-like Hall features in ultrathin SrRuO3/SrIrO3 are intrinsic skyrmion signals because the anomalous Hall sign stays negative, excluding two-channel superposition.","keywords":["SrRuO3","SrIrO3","topological Hall effect","anomalous Hall effect","skyrmions","Weyl points","ultrathin heterostructures","ARPES"],"falsifier":"A bare 20 u.c. SrIrO3 film measured under the same symmetrization should show no hump or anomalous Hall signal; if it does, the 20+n humps cannot be assigned to SrRuO3 skyrmions. A complementary check is whether a two-channel model with fixed total AHE sign can reproduce the n=6 and n=8 humps; if it can, the exclusion argument loses its force.","tokens_in":9321,"feed_emoji":"🧲","tokens_out":7929,"duration_ms":69780,"temperature":0.7,"pith_summary":"The paper sets out to settle whether hump-like features in the Hall effect of ultrathin SrRuO3 come from magnetic skyrmions or from a superposition of opposite anomalous Hall signals. Its strategy is to grow SrRuO3 on a thick SrIrO3 buffer, which keeps the ruthenate metallic and ferromagnetic down to one monolayer and fixes the anomalous Hall sign negative over a wide range of thickness and temperature. Hump-like features appear in the 20+6 and 20+8 heterostructures while the AHE sign stays negative, which the authors argue excludes the two-channel artifact. If the paper is right, the humps are intrinsic topological Hall signals and skyrmions exist in SrRuO3 at the few-unit-cell limit, opening a path to skyrmion devices in oxide heterostructures.","feed_headline":"Skyrmion Hall hump survives in SrRuO3 with fixed AHE sign","feed_subtitle":"Ultrathin SrRuO3 on SrIrO3 stays metallic to one monolayer and shows a topological Hall hump without an AHE sign flip.","key_machinery":"The central object is the [SrIrO3]20/[SrRuO3]n heterostructure. The 20-unit-cell SrIrO3 buffer supplies the interfacial doping and strain that keep SrRuO3 metallic and ferromagnetic down to one monolayer and, the authors argue, shift the band structure gradually with thickness so the anomalous Hall sign does not flip. That fixed sign is the identifying tool: when a hump-like feature appears in the symmetrized Hall loops of the n=6 and n=8 samples at fixed negative AHE, the two-channel superposition explanation is excluded. ARPES on the same type of stack tracks the X-M-X band crossing previously assigned to Weyl points, connecting the transport signature to momentum-space topology.","core_discovery":"The paper claims that a 20-unit-cell SrIrO3 buffer stabilizes a metallic ferromagnetic state in SrRuO3 down to n=1, that ARPES shows the topological band dispersion survives at these thicknesses, and that the anomalous Hall resistivity remains negative over n=1-8 and temperatures from 10 K to 90 K. In this regime, the n=6 and n=8 heterostructures show hump-like Hall features. Because the humps appear without any AHE sign change, the authors conclude the two-channel explanation -- a superposition of opposite AHE signals from different thickness or interface regions -- cannot produce them, and the humps are intrinsic topological Hall signals from magnetic skyrmions.","pith_inferences":["The paper's ARPES was taken on [SrIrO3]5/[SrRuO3]n stacks while transport used 20 u.c. buffers; a direct ARPES check on 20 u.c. buffers would close that transfer assumption.","If skyrmions are the cause, the hump amplitude should respond to the Dzyaloshinskii-Moriya interaction, which can be tuned by changing SrIrO3 thickness or strain; that prediction is not made in the paper.","The same fixed-AHE-sign test could be applied to other magnetic oxide thin-film systems where two-channel artifacts are debated.","A bare SrIrO3 control and an n=5-9 thickness map would sharpen the thickness window where the hump appears; the paper does not report them."],"forward_implications":["The topological band structure of SrRuO3 survives to the monolayer limit when interfaced with SrIrO3, so transport probes of Weyl and skyrmion physics become possible at two-dimensional thicknesses.","A Hall hump observed together with a fixed AHE sign can be used as a criterion for an intrinsic topological Hall effect in oxide heterostructures.","The thick SrIrO3 buffer extends itinerant ferromagnetism and metallicity below three unit cells, where single SrRuO3 films are insulating.","The 20+6 and 20+8 heterostructures are candidate few-unit-cell platforms for skyrmion-based spintronic devices."],"supporting_citations":[{"why":"Reports an interface-driven topological Hall effect in SrRuO3/SrIrO3 bilayers, the observation this paper extends and contrasts.","marker":"[8]"},{"why":"Identifies the X-M-X band crossing in SrRuO3 as Weyl points, the assignment the ARPES data rely on.","marker":"[12]"},{"why":"Earlier demonstration of electric-field-controlled anomalous and topological Hall effects in oxide bilayers, used as comparative thickness behavior.","marker":"[21]"},{"why":"Frames the controversy over whether Hall humps in SrRuO3 are chiral spin textures or artifacts; the paper positions against it.","marker":"[29]"},{"why":"Shows thickness inhomogeneity and Berry curvature engineering can produce AHE sign changes, the extrinsic alternative the paper excludes.","marker":"[34]"},{"why":"Proposes the two-channel anomalous Hall explanation for hump-like signals that the persistent negative AHE rules out.","marker":"[37]"},{"why":"Reports the metal-insulator transition in ultrathin SrRuO3 below 3-4 u.c. that the SrIrO3 buffer overcomes.","marker":"[40]"}],"fun_headline_variants":["Skyrmions persist in monolayer-thin SrRuO3 films","Monolayer SrRuO3 shows skyrmion Hall effect without AHE flip","Ultrathin SrRuO3 stays metallic and magnetic, skyrmions intact","No sign flip: topological Hall hump in SrRuO3 down to 1 layer","SrRuO3 ultrathin films reveal skyrmions via topological Hall"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The Hall signal measured on the full 20+n stack, after subtracting the normal Hall effect, is entirely attributable to the SrRuO3 layer, with the SrIrO3 buffer and the interface contributing no anomalous or topological Hall signal of their own.","fun_headline_variants_meta":{"raw":{"variants":["Skyrmions persist in monolayer-thin SrRuO3 films","Monolayer SrRuO3 shows skyrmion Hall effect without AHE flip","Ultrathin SrRuO3 stays metallic and magnetic, skyrmions intact","No sign flip: topological Hall hump in SrRuO3 down to 1 layer","SrRuO3 ultrathin films reveal skyrmions via topological Hall"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000616,"raw_usage":{"total_tokens":2835,"prompt_tokens":894,"completion_tokens":1941,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":510,"completion_tokens_details":{"reasoning_tokens":1845}},"tokens_in":510,"tokens_out":1941,"duration_ms":14068,"temperature":1.0,"reasoning_tokens":1845,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T15:03:45.014761+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A bare 20 u.c. SrIrO3 film measured under the same symmetrization should show no hump or anomalous Hall signal; if it does, the 20+n humps cannot be assigned to SrRuO3 skyrmions. A complementary check is whether a two-channel model with fixed total AHE sign can reproduce the n=6 and n=8 humps; if it can, the exclusion argument loses its force.","supporting_citations":[{"cited_title":"Matsuno, N","cited_arxiv_id":null,"evidence_quote":"Reports an interface-driven topological Hall effect in SrRuO3/SrIrO3 bilayers, the observation this paper extends and contrasts."},{"cited_title":"Lin et al., Electric Field Control of the Magnetic Weyl Fermion in an Epitaxial SrRuO3(111) Thin Film, Adv","cited_arxiv_id":null,"evidence_quote":"Identifies the X-M-X band crossing in SrRuO3 as Weyl points, the assignment the ARPES data rely on."},{"cited_title":"Ohuchi, J","cited_arxiv_id":null,"evidence_quote":"Earlier demonstration of electric-field-controlled anomalous and topological Hall effects in oxide bilayers, used as comparative thickness behavior."},{"cited_title":"Kimbell, C","cited_arxiv_id":null,"evidence_quote":"Frames the controversy over whether Hall humps in SrRuO3 are chiral spin textures or artifacts; the paper positions against it."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Shows thickness inhomogeneity and Berry curvature engineering can produce AHE sign changes, the extrinsic alternative the paper excludes."},{"cited_title":"Kimbell, P","cited_arxiv_id":null,"evidence_quote":"Proposes the two-channel anomalous Hall explanation for hump-like signals that the persistent negative AHE rules out."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Reports the metal-insulator transition in ultrathin SrRuO3 below 3-4 u.c. that the SrIrO3 buffer overcomes."}],"review_version":1}