{"id":"efacb66d-cf3a-4483-a7e4-1f1766870ba9","arxiv_id":"2608.02501","paper_version":1,"verdict":"CONDITIONAL","confidence":"LOW","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"Eight LSCO/LCO superlattices measured up to 72 T show a superconducting dome whose upper critical field and coherence length are claimed to confirm the Bianconi–Perali–Valletta shape-resonance theory.","lead":"This paper reports pulsed-field transport measurements up to 72 T on eight artificial LSCO/LCO superconducting superlattices and claims the data confirm a 1996 theory in which the superconducting dome arises from a Fano–Feshbach shape resonance between two pairing regimes. If correct, it would show that layer-thickness geometry, not chemical doping, can be used as the control knob for high-temperature superconductivity.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The unverified δ = 0.45(1−L/d) calibration is load-bearing: every quantitative claim about the dome and its BPV overlay uses this relation, yet the text's own numbers are inconsistent and no direct carrier-density measurement is provided.","rationale":"The paper's biggest strength is a systematic high-field dataset and a clear falsifiable geometric-control picture; I do not doubt the measurements themselves. But the argument that these data validate BPV theory is quantitative: the experimental dome must match the theoretical dome on the same doping scale. The only such scale provided is δ=0.45(1−L/d). This relation is asserted, not derived; the paper does not cite prior direct measurements of carrier density in these superlattices, and the internal inconsistencies in the reported peak positions/dopings show that even the authors' own use of the relation is unstable. If the relation is wrong, every downstream conclusion—BEC-like underdoped side, BCS-like overdoped side, peak at the 'magic ratio' 2/3—could be an artifact of an incorrect abscissa. A Hall or XAS measurement would settle this. Since the reader already flagged this calibration as the weakest assumption and recommended conditional acceptance with additional measurements, my read agrees and does not move the verdict.","tokens_in":15075,"tokens_out":15002,"duration_ms":172560,"concrete_test":"Measure the low-temperature Hall coefficient on the same eight superlattices in the normal state (μ0H > μ0Hc2, T just above Tc) and compute the hole density n_H; compare n_H to 0.45(1−L/d). If the Hall number deviates nonlinearly from the linear relation, or the deviations exceed the resolution needed to locate the TC peak, recompute the dome and the BPV overlay on the measured doping axis and check whether the peak at L/d=2/3 (or 0.75) and the BEC-BCS crossover survive.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central validation claim rests on the relation δ = 0.45(1−L/d) introduced in §2 as a 'formal doping' with no derivation or direct measurement. Every quantitative result—peak location δ≈0.11, IMT at δ≈0.15, the BPV overlays in Fig. 8, and the BEC-BCS crossover assignment—is expressed through this conversion. If the charge transfer from the La1.55Sr0.45CuO4 spacers into the La2CuO4 wells is incomplete, non-uniform, or L/d-dependent, then the dome is not actually mapped onto the doping axis of the BPV theory, and the claimed validation loses quantitative footing. The concern is not purely hypothetical: Fig. 1c's stated optimum 0.66<L/d<0.7 would, by the same relation, correspond to δ≈0.135–0.153, not the printed '0.10–0.12', while the abstract/main text state the maximum is at L/d≈0.75. The relation also needs justification as the relevant well doping rather than a whole-superlattice average. A direct carrier-density measurement is required.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports pulsed-field (up to 72 T) magnetotransport measurements on MBE-grown LSCO/LCO artificial superlattices with eight values of the geometrical ratio L/d. It extracts TC, the upper critical field μ0Hc2(0) using 50% and 100% resistance criteria, the Ginzburg-Landau coherence length ξ0, and parameters of a Kondo plus Planckian fit to the normal-state resistance. The central claim is that TC and μ0Hc2(0) peak near L/d ≈ 0.75 while TCξ0 peaks at L/d = 2/3, revealing a BEC-to-BCS crossover across the superconducting dome, and that this evolution validates the Bianconi-Perali-Valletta (BPV) Fano-Feshbach shape-resonance theory. All quantitative comparisons are expressed through the effective doping relation δ = 0.45(1 − L/d).","tokens_in":15464,"tokens_out":4468,"duration_ms":52150,"significance":"The raw magnetotransport data are a useful and independent contribution: the measurements are not constructed from the theory, the 50%/100% resistance criteria for Hc2 are standard, and upward curvature of μ0Hc2(T) across a wide doping range is a genuine multiband indicator. The data set also covers the full superconducting dome of this heterostructure family, which is of interest for quantum-design approaches to superconductivity. However, the paper's main quantitative claim — the shape and position of the doping axis, the BEC-BCS crossover assignment, and the quantitative overlay with BPV theory — rests on an unverified and, in places, internally inconsistent doping calibration. The significance is therefore conditional: if the δ(L/d) mapping and the sample-to-sample reproducibility were established, the result would be important; at present it is not quantitatively established.","major_comments":[{"comment":"The relation ⟨δ⟩ = 0.45(1 − L/d) is load-bearing: every quantitative statement — peak location δ ≈ 0.11, IMT at δ ≈ 0.15, Fig. 7(b), and the BPV overlays in Fig. 8 — is expressed through this conversion. No derivation, calibration, or direct carrier-density measurement is given. The text itself is internally inconsistent: Fig. 1(c) states the optimum is 0.66 < L/d < 0.7 and assigns it δ = 0.10–0.12, but the stated relation gives δ ≈ 0.135–0.153 for that interval; the abstract places the maximum at L/d ≈ 0.75, i.e., δ ≈ 0.11. The relation also conflates the hole density in the LCO wells with a whole-superlattice average and assumes complete, linear charge transfer from the La1.55Sr0.45CuO4 spacers. This is the central axis of the paper and needs direct validation or an explicit error analysis.","section":"§2, 'Materials' (δ = 0.45(1 − L/d))"},{"comment":"The central claim of 'compelling experimental validation' of BPV theory is supported by overlaying theoretical dome colormaps from ref. [55] on the experimental TC and μ0Hc2(0) data. However, the manuscript does not state how the theory curves were normalized, what parameter set was used, or how the horizontal axis of the theory domes is registered with the experimental δ axis. No residual or goodness-of-fit quantification is provided. Since ref. [55] is from the same group, the comparison risks being a visual overlay rather than a falsifiable test. Please define the quantitative comparison protocol, including the doping mapping of the theory curves and the uncertainty in the overlay.","section":"§4, Fig. 8(a,b)"},{"comment":"No error bars, sample-to-sample spread, or reproducibility information is reported for TC, μ0Hc2(0), or ξ0. The abstract says TC peaks at L/d ≈ 0.75, whereas Fig. 1(c) places the maximum in 0.66 < L/d < 0.7; without uncertainty estimates these two statements are not necessarily in conflict, but the claimed precision of the peak position cannot be evaluated. Similarly, the extraction of ξ0 by extrapolating ξ(T → 0) in Fig. 7 needs a stated extrapolation procedure and uncertainty. At minimum, the authors should report the spread of repeated samples or state explicitly whether only one sample per L/d was measured.","section":"Figs. 1, 6, 7 and abstract"}],"minor_comments":[{"comment":"The equation for the normal-state resistance is garbled in the text ('!#', '#%&', superscripts). It must be typeset correctly, with all fitting parameters (TK, R0k, r0, A, B) defined in the text or caption.","section":"Eq. (1)"},{"comment":"The text refers to 'Fig. 6(c)-(f)', but the figure as presented has only panels (a) and (b). Update the callout or the figure.","section":"Fig. 6 callout in §4"},{"comment":"The text says 'plotted in Fig. 6(b)' but the coherence length as a function of L/d and δ is in Fig. 7(b). This should be corrected.","section":"Fig. 7(b) callout in §4"},{"comment":"Fig. 8(d) plots TC/(μ0Hc2(0)) ∝ TCξ0, but it should state which Hc2 criterion (H50 or H100) was used. Also, the 'irreversibility field μ0Hcirr' in Fig. 5 is used without defining its measurement criterion.","section":"Fig. 8(d) and Fig. 5"},{"comment":"The sentence mentioning 'Ayres experimental results on two components in the strange metal phase [66,67]' appears to cite the wrong references: [66] is Wahlberg et al., and [67] is Ayres et al. Please correct the citation.","section":"References in conclusions"}],"recommendation":"major_revision","confidential_remarks":"The datataking and the magnetotransport analysis look competent, and the upward curvature of Hc2(T) is a solid experimental observation. The problem is the horizontal axis: everything quantitative depends on δ = 0.45(1 − L/d), which is introduced as a 'formal doping' without direct measurement and with internal inconsistencies. I would be willing to reconsider after a revision that either calibrates the doping axis directly (Hall, X-ray absorption, or a documented charge-transfer model with independent verification) or explicitly restricts the claims to L/d without the δ mapping. As it stands, the paper overstates the ‘experimental validation’ of BPV theory."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Two things to know upfront. First, this is a genuinely new experimental dataset: eight LSCO/LCO superlattices spanning the full dome, with Hc2(T) to 72 T and a systematic ξ0 extraction. Second, the paper's central 'validation' of BPV theory rests on a doping calibration that is asserted, not measured, and there is an internal contradiction in the dome peak position that a referee will catch quickly.\n\nThe data acquisition looks standard and the upward curvature of Hc2(T) across all samples is a reasonable multiband indicator. The clean platform — stoichiometric LCO wells, no chemical disorder — is a real advantage over bulk cuprates. The TCξ0 peak at L/d = 2/3 is an interesting new observable, and the isosbestic crossing in R(H) for underdoped samples is worth further study.\n\nThe biggest problem is δ = 0.45(1 - L/d). No derivation, no direct carrier density measurement. If charge transfer is incomplete or nonlinear in L/d, every quantitative statement about the doping axis — the IMT at δ≈0.15, the BEC-BCS crossover, the comparison to BPV theory — loses its footing. The paper itself is inconsistent: Fig. 1c says the optimum is 0.66 < L/d < 0.7, which by their own formula is δ ≈ 0.135–0.153, but the text says δ ≈ 0.10–0.12; the abstract and conclusions say L/d ≈ 0.75. These numbers need to be reconciled.\n\nThere is also a mathematical slip in Sec. 4: they claim TC/μ0Hc2(0) ∝ TCξ0, but from their own Eq. 2, ξ0 ∝ 1/√Hc2, so TCξ0 ∝ TC/√Hc2, not TC/Hc2. Unless they plot something else, the claimed TCξ0 peak at 2/3 is not what the data show.\n\nMinor but worth noting: no error bars on TC, Hc2(0), or ξ0; no sample-to-sample spread; and the theoretical overlay is from the authors' own group (ref 55). That doesn't make the data circular, but 'validation' is a strong word for comparison with your own calculation.\n\nThis paper deserves a serious referee — the dataset is important and the platform is cleaner than bulk cuprates. But it needs major revision before I'd trust the interpretation: direct Hall or X-ray absorption measurements of the well doping, error bars, a corrected proportionality, and a reconciled dome peak. If those are addressed, it could be a solid contribution.","headline":"A useful full-dome Hc2 dataset in artificial cuprate superlattices, but the 'validation' claim rests on an asserted doping relation and the paper's own numbers don't align.","tokens_in":15981,"tokens_out":6971,"would_cite":true,"duration_ms":66342,"reading_group":"maybe","serious_thinker":"no","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["74.25.Dw","74.25.Op","74.78.Fk","74.20.Mn"],"model":"deepseek-v4-flash","headline":"In artificial superconducting superlattices, the entire dome of critical temperature versus doping can be produced by a single geometric ratio L/d, and the data point to a Fano-Feshbach shape resonance between two paired condensates.","keywords":["superconducting dome","artificial superlattices","Fano-Feshbach shape resonance","BEC-BCS crossover","upper critical field","multiband superconductivity","coherence length","cuprate heterostructures"],"falsifier":"Measure the actual carrier density in the La2CuO4 wells as a function of L/d (for example, by Hall effect, angle-resolved photoemission, or resonant x-ray scattering) and compare it with δ=0.45(1-L/d). If the relation fails significantly, or if a sample with a given L/d but different absolute layer thicknesses L and W shows a different TC, the geometric-tuning interpretation would need revision.","tokens_in":14964,"feed_emoji":"🧲","tokens_out":6943,"duration_ms":67453,"temperature":0.7,"pith_summary":"This paper reports that the entire superconducting dome—the rise, peak, and fall of the critical temperature as carrier density is varied—can be reproduced in artificial superlattices by changing a single geometric parameter: the ratio L/d between the thickness L of superconducting quantum wells and the superlattice period d. The authors measure transport in a series of lanthanum-cuprate multilayers under pulsed magnetic fields up to 72 T and find that both the critical temperature and the upper critical field peak at L/d ≈ 0.75, while the product of critical temperature and coherence length peaks at the magic ratio L/d = 2/3. They interpret this as evidence for a Fano-Feshbach shape resonance: a resonant transfer of Cooper pairs between two superconducting condensates, one in the BCS regime and one in the BEC-BCS crossover, triggered by a Lifshitz electronic transition. If correct, this would show that high-temperature superconductivity can be engineered by geometry rather than chemical doping alone, and that the underdoped side of the dome is intrinsically strongly paired rather than degraded by competing order.","feed_headline":"One geometric ratio sets the superconductivity dome","feed_subtitle":"New magneto-transport data on cuprate superlattices put the dome's peak at L/d≈0.75, while stability peaks at 2/3.","key_machinery":"The central mechanism is the Fano-Feshbach shape resonance: a resonant enhancement of the inter-band pair-transfer coupling that occurs when the chemical potential is tuned near a Lifshitz transition (a topological change of the Fermi surface) in a superlattice of quantum wells. In this system, the tuning is achieved not by chemical substitution but by the geometric ratio L/d, which controls quantum confinement and the charge transferred from the metallic spacers into the superconducting layers. The resonance couples a BCS-like condensate (large coherence length) with a BEC-like condensate (strong pairing), and the theory predicts that the maximum critical temperature occurs when the second","core_discovery":"The paper's central claim is that the superconducting dome in these artificial superlattices is governed by the quantum-geometric parameter L/d. By varying L/d, the authors map transport across the full dome and find that TC and μ0HC2 peak at L/d≈0.75 while TCξ0 peaks at L/d=2/3. The upward curvature of μ0HC2(T) for all samples indicates persistent multiband superconductivity. The authors interpret the systematic decrease of ξ0 toward the underdoped side and the peak of TCξ0 at the Lifshitz transition as a BEC-to-BCS crossover, which they argue is the signature of a Fano-Feshbach shape resonance between two paired condensates.","pith_inferences":["If charge transfer from the metallic spacers is not simply proportional to 1-L/d, the doping axis itself shifts; a direct measurement of the carrier density in the wells (e.g., by Hall effect or resonant scattering) would test whether the dome is truly a function of hole concentration or of confinement alone.","The same geometric tuning might be applied to other doped-Mott-insulator/overdoped-metal pairs; the theory predicts the magic ratio L/d=2/3 should be universal, so testing with different spacer materials would distinguish the shape-resonance mechanism from material-specific effects.","The absence of CDW competition in these clean heterostructures suggests that the underdoped BEC-like regime is an intrinsic strong-pairing state; one could look for telltale signatures such as a closing of the single-particle gap or a flattening of the superfluid stiffness that would distinguish BEC-like pairing from disorder-induced localization.","The upward curvature of μ0HC2(T) is taken as evidence of multiband superconductivity; a direct spectroscopic probe of two distinct gaps (e.g., tunneling or angle-resolved photoemission) across the entire L/d range would confirm that the second subband actually crosses the Fermi level at the claimed magic ratio."],"forward_implications":["The maximum critical temperature in these artificial superlattices occurs at L/d≈0.75 (δ≈0.11), shifted from the natural cuprate optimum near δ≈0.15, and is accompanied by a peak in the upper critical field.","Multiband superconductivity persists across the entire dome, as evidenced by the upward curvature of μ0HC2(T) in all samples, in contrast to single-band Werthamer-Helfand-Hohenberg behavior.","The underdoped side of the dome is not dominated by charge-density-wave competition; instead it shows enhanced μ0HC2(0) and short coherence length, suggesting strong BEC-like pairing.","The transport regimes cross over from a Kondo-like pseudogap (δ<0.15) to a Planckian strange metal at δ≈0.15, which is a lower doping than in natural cuprates (δ≈0.18).","The product TCξ0 peaks at L/d=2/3, matching the predicted Lifshitz transition for the second subband."],"fun_headline_variants":["Geometric ratio L/d shapes the superconducting dome","L/d ratio controls high-Tc dome in artificial superlattices","Fano-Feshbach resonance drives superconducting dome in layered cuprates","Quantum well geometry dictates superconducting dome peak"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The entire mapping of the experimental dome onto the theory relies on the assumed linear relation between the geometric parameter and the hole doping, δ=0.45(1-L/d), which is stated without a direct measurement of the carrier density in the superconducting wells; if the actual charge transfer differs, or is nonlinear in L/d, the claimed correspondence between the measured dome and the calculated dome loses its quantitative footing.","fun_headline_variants_meta":{"raw":{"variants":["Geometric ratio L/d shapes the superconducting dome","L/d ratio controls high-Tc dome in artificial superlattices","Fano-Feshbach resonance drives superconducting dome in layered cuprates","Quantum well geometry dictates superconducting dome peak"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000603,"raw_usage":{"total_tokens":2677,"prompt_tokens":799,"completion_tokens":1878,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":543,"completion_tokens_details":{"reasoning_tokens":1812}},"tokens_in":543,"tokens_out":1878,"duration_ms":15671,"temperature":1.0,"reasoning_tokens":1812,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-04T06:00:24.663347+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the actual carrier density in the La2CuO4 wells as a function of L/d (for example, by Hall effect, angle-resolved photoemission, or resonant x-ray scattering) and compare it with δ=0.45(1-L/d). If the relation fails significantly, or if a sample with a given L/d but different absolute layer thicknesses L and W shows a different TC, the geometric-tuning interpretation would need revision.","supporting_citations":[],"review_version":1}