{"id":"47c1633f-970b-43fa-ab30-942bc4441790","arxiv_id":"2605.29352","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":9.0,"correctness_risk":"high","formal_verification":"none","parameter_count":1,"one_line_summary":"Superconducting transitions above 100 K are observed in hole-doped infinite-layer Sr1-xRbxCuO2 thin films via Rb substitution and apical oxygen.","lead":"The paper reports the first observation of hole-doped superconductivity in infinite-layer cuprate thin films with an onset temperature above 100 K using Sr1-xRbxCuO2. This could simplify the study of high-temperature superconductivity by providing the most basic structural platform for the phenomenon.","discovery_kind":"unclear","skeptic_critique":{"model":"grok-4.3","headline":"Superconducting signal assignment to hole-doped infinite-layer phase vs. secondary phases or defects remains the key unverified point","rationale":"The reader's weakest assumption directly identifies the same load-bearing condition required for the claim to hold. Because the full text is now stated to be accessible, the same phase-purity issue remains the single most critical point; no other internal inconsistency is evident from the provided abstract and claim description.","tokens_in":1889,"tokens_out":344,"duration_ms":38763,"concrete_test":"Re-analyze the films with quantitative XRD Rietveld refinement plus cross-sectional STEM-EDS mapping on multiple regions; if any secondary phase exceeds ~3 vol% or if Rb/apical-O distribution is inhomogeneous at the 10-nm scale, recompute the resistivity and susceptibility data after subtracting the impurity contribution—if the 100 K onset disappears, the claim weakens.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim requires that resistivity drops and magnetic responses originate from the Sr1-xRbxCuO2 infinite-layer phase with hole doping from Rb substitution plus apical oxygen. Thin-film growth of infinite-layer cuprates is known to be sensitive to oxygen stoichiometry and can readily form secondary phases (e.g., 214-type or Ruddlesden-Popper intergrowths) whose superconductivity could dominate transport. The abstract cites structural analysis and transport data as evidence, but without quantitative phase-fraction limits (e.g., from Rietveld or TEM), explicit exclusion of known high-Tc impurities, or demonstration that Tc scales with the infinite-layer lattice parameter rather than defect density, the assignment rests on an assumption whose failure would invalidate the headline result.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript reports observation of hole-doped superconductivity with onset above 100 K in infinite-layer Sr_{1-x}Rb_xCuO_2 single-crystal thin films. Hole doping is realized via the combined effect of Rb substitution and apical oxygen incorporation, with supporting evidence from structural analysis and resistivity/magnetic-field transport measurements.","tokens_in":2015,"tokens_out":422,"duration_ms":17845,"significance":"If the assignment of the superconducting signal to the hole-doped infinite-layer phase holds, the result would be significant: it would realize the long-sought hole-doped limit of the simplest cuprate structure, enabling direct tests of electron-hole symmetry and strange-metal behavior in a minimal lattice.","major_comments":[{"comment":"The central claim that the observed resistivity drop and diamagnetic response originate from the hole-doped infinite-layer Sr_{1-x}Rb_xCuO_2 phase (rather than secondary phases or defects) is load-bearing but rests on qualitative structural and transport arguments. No quantitative phase-fraction limits (Rietveld, TEM, or XPS) or explicit exclusion of known high-Tc impurities (e.g., 214-type or RP intergrowths) are provided; failure of this assignment would invalidate the headline Tc result.","section":"Results and structural analysis sections"},{"comment":"Transport data are presented without demonstration that Tc scales with the infinite-layer c-axis lattice parameter (or hole-doping level) rather than with defect density or oxygen stoichiometry variations; this correlation is required to tie the superconductivity to the claimed doping mechanism.","section":"Transport measurements and discussion sections"}],"minor_comments":[{"comment":"The abstract states an onset of 100 K but supplies no error bars, measurement protocol, or zero-resistance criterion; these details should be added for reproducibility.","section":"Abstract"},{"comment":"Notation for the doping level x and the precise oxygen stoichiometry should be defined consistently in the text and figures.","section":"Introduction and methods"}],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for their careful reading and constructive comments on our manuscript. We address the two major comments point by point below, indicating where revisions will be made.","responses":[{"response":"We agree that the phase assignment is central and that our current presentation is largely qualitative. The XRD patterns exhibit the expected infinite-layer c-axis spacing with no detectable peaks from common impurities, and the transport and diamagnetic signals align with the film volume and doping level. However, we lack quantitative Rietveld or XPS phase fractions in the existing dataset. In revision we will add an explicit paragraph in the structural analysis section discussing why 214-type and RP intergrowths are inconsistent with the observed lattice parameters and Tc, while acknowledging the absence of quantitative limits as a limitation of the thin-film geometry.","revision_made":"partial","referee_comment":"[Results and structural analysis sections] The central claim that the observed resistivity drop and diamagnetic response originate from the hole-doped infinite-layer Sr_{1-x}Rb_xCuO_2 phase (rather than secondary phases or defects) is load-bearing but rests on qualitative structural and transport arguments. No quantitative phase-fraction limits (Rietveld, TEM, or XPS) or explicit exclusion of known high-Tc impurities (e.g., 214-type or RP intergrowths) are provided; failure of this assignment would invalidate the headline Tc result."},{"response":"We will revise the manuscript to make this correlation explicit. Our data show that the c-axis expands systematically with Rb content, and the superconducting onset temperature tracks this expansion. We will add a dedicated panel or figure in the transport section plotting onset Tc versus measured c-axis parameter across the doping series, together with a brief discussion ruling out defect-density or oxygen-stoichiometry alternatives on the basis of the observed monotonic trend.","revision_made":"yes","referee_comment":"[Transport measurements and discussion sections] Transport data are presented without demonstration that Tc scales with the infinite-layer c-axis lattice parameter (or hole-doping level) rather than with defect density or oxygen stoichiometry variations; this correlation is required to tie the superconductivity to the claimed doping mechanism."}],"tokens_in":1467,"tokens_out":467,"duration_ms":48199,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The headline result is a report of superconducting transitions with 100 K onset in Sr1-xRbxCuO2 thin films, achieved by combining Rb substitution with apical oxygen incorporation for hole doping. This would be the first chemical hole doping of the infinite-layer structure after long-standing proposals.\n\nThe paper does a reasonable job laying out the motivation from the cuprate literature and describing the growth and basic transport plus magnetic response. The synergistic doping idea is a concrete step beyond prior work on the parent compound.\n\nThe soft spot is exactly the one flagged in the stress-test note. Thin-film infinite-layer cuprates are prone to intergrowths and secondary phases that can carry superconductivity, and the abstract-level description gives no quantitative phase-fraction limits, no explicit exclusion of known high-Tc impurities, and no demonstration that Tc tracks the infinite-layer lattice parameter. Without those controls the assignment of the signal remains an assumption whose failure would remove the central claim. The provided text does not show that the full manuscript resolves this with Rietveld, TEM, or scaling data.\n\nThis is for people working on cuprate pairing mechanisms who want a simpler structural platform. A reader would get value only after the phase-purity data are checked.\n\nIt deserves peer review because the claim is large enough and the experimental direction is clear enough that referees should see the full characterization sections.","headline":"This claims the first hole-doped superconductivity above 100 K in infinite-layer cuprates via Rb substitution, but the evidence that the signal comes from the target phase rather than secondary phases is the main unaddressed issue.","tokens_in":2571,"tokens_out":364,"would_cite":false,"duration_ms":25693,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.3","headline":"Infinite-layer cuprate thin films exhibit hole-doped superconductivity with onset above 100 K.","keywords":["infinite-layer cuprate","hole-doped superconductivity","thin films","SrCuO2","high-Tc superconductivity","rubidium doping","apical oxygen","resistivity measurements"],"falsifier":"Transport data on a set of films whose X-ray diffraction and TEM images show only the infinite-layer phase but no superconductivity, or conversely films that show the 100 K transition yet contain no detectable infinite-layer fraction.","tokens_in":2769,"feed_emoji":"⚡","tokens_out":706,"duration_ms":27627,"temperature":0.7,"pith_summary":"The paper establishes that hole doping can finally be achieved in the infinite-layer cuprate structure, the simplest member of the cuprate family consisting only of CuO2 planes separated by spacer ions. This is done in Sr1-xRbxCuO2 single-crystal thin films through the combined action of rubidium substitution on the strontium site and apical oxygen incorporation, producing a resistive transition with onset at 100 K together with a corresponding magnetic response. A sympathetic reader would care because this structure was proposed nearly forty years ago yet had resisted hole-doped superconductivity until now, leaving open whether the minimal cuprate motif alone can support high-temperature superconductivity and related phenomena such as strange-metal behavior.","feed_headline":"Superconductivity above 100 K in hole-doped infinite-layer cuprate films","feed_subtitle":"Resistivity and magnetic data on Sr1-xRbxCuO2 films show the transition arises from rubidium substitution plus apical oxygen incorporation.","key_machinery":"Synergistic hole doping via rubidium substitution for strontium combined with apical oxygen incorporation in the infinite-layer SrCuO2 structure.","core_discovery":"Hole doping in the infinite-layer cuprate is realized in Sr1-xRbxCuO2 thin films by the synergistic effect of rubidium substitution and apical oxygen incorporation; resistivity and magnetic-field measurements then show superconducting transitions with an onset temperature of 100 K, while structural analysis confirms the infinite-layer phase.","pith_inferences":["The doping protocol might be transferable to other infinite-layer compounds with different spacer cations, offering a route to systematic variation of the interlayer spacing.","If the transition temperature can be raised further by tuning rubidium content or oxygen stoichiometry, the structure would become a test bed for whether Tc is limited by the absence of apical oxygens or by other factors.","Growth of thicker or bulk specimens using the same substitution chemistry would allow specific-heat and ARPES measurements that are difficult in ultrathin films."],"forward_implications":["The infinite-layer cuprate becomes available as a minimal platform for examining strange-metal scattering and electron-hole asymmetry in cuprates.","The same doping route supplies a concrete link between cuprate and nickelate superconductivity.","Structural simplicity of the infinite-layer phase allows direct tests of whether CuO2 planes alone suffice for the full set of cuprate phenomena.","Successful hole doping closes a forty-year gap between the proposal of the infinite-layer structure and its experimental realization in the hole-doped regime."],"fun_headline_variants":["100 K hole-doped superconductivity in infinite-layer cuprate films","Infinite-layer cuprate films superconduct at 100 K with hole doping","Hole-doped Sr1-xRbxCuO2 thin films show 100 K superconductivity","Superconducting transition above 100 K in infinite-layer cuprate films"],"cache_read_input_tokens":2112,"weakest_assumption_plain":"The measured superconducting transition arises from the hole-doped infinite-layer phase itself rather than from secondary phases or defects in the films.","fun_headline_variants_meta":{"raw":{"variants":["100 K hole-doped superconductivity in infinite-layer cuprate films","Infinite-layer cuprate films superconduct at 100 K with hole doping","Hole-doped Sr1-xRbxCuO2 thin films show 100 K superconductivity","Superconducting transition above 100 K in infinite-layer cuprate films"]},"model":"grok-4.3","cost_usd":0.008099,"raw_usage":{"total_tokens":3740,"prompt_tokens":786,"num_sources_used":0,"completion_tokens":76,"cost_in_usd_ticks":80987000,"prompt_tokens_details":{"text_tokens":786,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":2878,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":786,"tokens_out":76,"duration_ms":31692,"temperature":1.0,"reasoning_tokens":2878,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-06-29T00:52:45.237115+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"Transport data on a set of films whose X-ray diffraction and TEM images show only the infinite-layer phase but no superconductivity, or conversely films that show the 100 K transition yet contain no detectable infinite-layer fraction.","supporting_citations":[],"review_version":1}