{"id":"d885c6d1-9955-41fe-9931-aa786d4814ba","arxiv_id":"2608.02042","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"La0.8Sr0.2NiO2 membranes remain superconducting up to 210 GPa, with a dome-shaped Tconset peaking at 74.5 K at 146 GPa.","lead":"Freestanding nickelate superconducting membranes kept their resistance drop all the way to 210 GPa, peaking at 74.5 K near 146 GPa before slowly declining. The measurement maps how extreme pressure changes a nickel-oxide superconductor and constrains what controls its pairing.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"210 GPa persistence rests on a single-sample 99.5%-onset resistance drop with no zero-resistance, field-suppression, or local-pressure check at that pressure; broadening/contact artifacts are not excluded.","rationale":"The reader's weakest assumption is exactly the load-bearing point here: the high-pressure conclusion depends on identifying a 99.5% resistance-drop onset as bulk superconductivity, in a regime where no zero-resistance or field-suppression data exist and where non-hydrostatic conditions could create artifacts. My independent stress-test reaches the same conclusion from the paper's own text: Tconset is defined by a 0.5% drop; the only field data near high pressure are at 80 GPa; the derivative Tcm is only shown up to 147 GPa; and at 146 GPa the gap between Tconset and Tc2-line is already 10 K. The 210 GPa point is therefore under-supported, but not contradicted by any internal inconsistency or external consensus. Since the reader already assigned CONDITIONAL, my concern does not change the verdict; it reinforces the need for the specific missing data (zero resistance, field suppression, derivative analysis, local pressure determination) before the 'superconductivity persists to 210 GPa' headline can be accepted at face value.","tokens_in":10894,"tokens_out":5028,"duration_ms":49629,"concrete_test":"Re-examine the raw R(T) trace for S#3 at 174, 192, and 210 GPa and evaluate three criteria at each pressure: (i) T_zero where R reaches the measurement noise floor; (ii) T_m from the derivative maximum (same method as Fig. 3); (iii) the shift of the entire resistance drop under an applied 5–7 T magnetic field at 210 GPa. If no zero resistance, no derivative peak near Tconset, or no field-induced suppression is observed, the 210 GPa persistence claim should be downgraded to 'a 0.5% resistive anomaly at 57.4 K.'","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim that superconductivity persists up to 210 GPa is supported by exactly one resistance-drop onset in S#3 at 210 GPa (Tconset ≈ 57.4 K, defined as the 99.5% R point). No zero-resistance state is reported above 174 GPa, no magnetic-field suppression is shown above 80 GPa (Fig. 4a is only S#2 at 80 GPa), and the derivative/midpoint analysis in Fig. 3 is confined to S#1 up to 147 GPa. Thus the ultrahigh-pressure point rests on the assumption that a 0.5% resistance drop represents the onset of bulk superconductivity. The paper itself shows how broad the transition is: at 146 GPa, Tc99.5%R = 74.5 K while Tc2-line = 64 K, a 10 K gap. If broadening continues to 210 GPa, the 99.5% criterion can be met at a temperature far above any bulk coherent transition, or by a filamentary/degraded region. Silicone oil solidifies at much lower pressure and is not hydrostatic at 210 GPa, so the diamond-Raman pressure may not equal the local pressure at the membrane; microcracks or electrode-contact changes under non-hydrostatic stress could produce spurious resistance anomalies. None of the supplementary raw data or error bars are available to test this. This is not a demonstrated false claim, but it is the weakest load-bearing step.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports high-pressure electrical resistance measurements on freestanding La0.8Sr0.2NiO2 infinite-layer nickelate membranes mounted on diamond anvil culets. Using Tconset defined as the 99.5% resistance point, the authors find a dome-like pressure dependence: Tconset increases from about 16 K at ambient pressure to a maximum of 74.5 K at 146 GPa, then decreases to 57.4 K at 210 GPa. Three samples (S#1, S#2, S#3) show broadly consistent behavior up to 165 GPa, with S#3 extending to 210 GPa. Additional evidence includes magnetic-field suppression of the resistance drop at 80 GPa and a derivative-based midpoint analysis for S#1 up to 147 GPa. The authors conclude that superconductivity in this nickelate persists to much higher pressures than in cuprates and other oxide superconductors, and they place the results in a comparative phase diagram.","tokens_in":11213,"tokens_out":2631,"duration_ms":29169,"significance":"If correct, the result is significant: it would establish that infinite-layer nickelate superconductivity survives to 210 GPa, well beyond the pressure range where cuprate superconductivity is typically suppressed, and it would provide a clear experimental target for theories of nickelate pairing under extreme compression. The paper has notable strengths: three independent samples reproduce the rising Tconset(P) trend; magnetic-field suppression at 80 GPa supports the superconducting origin of the resistance drop; and the derivative analysis in Fig. 3 partially addresses the transition-broadening concern. However, the central claim of persistence to 210 GPa rests on a single 99.5%-onset resistance drop at that pressure, with no zero-resistance state, no field suppression, and no broadening analysis at the highest pressures. The non-hydrostatic pressure medium and the absence of pressure uncertainties further weaken the quantitative phase diagram. These issues are load-bearing and need to be addressed before the claim can be accepted.","major_comments":[{"comment":"The claim that superconductivity persists to 210 GPa rests entirely on S#3 at P = 210 GPa showing a 99.5%-resistance-drop onset of 57.4 K. No zero-resistance state is reported above 174 GPa, field-suppression data are shown only for S#2 at 80 GPa (Fig. 4a), and the derivative/midpoint analysis that rules out pure transition broadening is limited to S#1 up to 147 GPa (Fig. 3). Given that the paper itself emphasizes how broad the transitions are (at 146 GPa, Tc99.5%R = 74.5 K while Tc2-line = 64 K), the 210 GPa point could in principle reflect a broadened tail or a filamentary/contact artifact rather than bulk superconductivity. The authors should show full R(T) curves at 174–210 GPa, provide midpoint/offset or other bulk-sensitive Tc estimates at those pressures, and quantify how the transition width evolves beyond 147 GPa. Alternatively, additional evidence such as field suppression at t","section":"§2, Fig. 2f; Fig. 4; Fig. 3"},{"comment":"Silicone oil is used as the pressure-transmitting medium for all measurements. Silicone oil solidifies below 10 GPa and is strongly non-hydrostatic at 210 GPa. The sample pressure is determined from diamond Raman spectroscopy, but no error bars are given, and the local pressure experienced by the membrane on the diamond culet may differ from the Raman-determined pressure, especially under non-hydrostatic conditions. This is load-bearing for the quantitative P-Tconset phase diagram and for the claimed maximum at 146 GPa and the dome shape. The authors should state the estimated pressure uncertainty, discuss possible pressure gradients across the membrane, and indicate whether any local pressure marker or post-run pressure check was performed.","section":"Methods: Pressure Transmitting Medium and Determination"},{"comment":"The paper claims a 'continuous dome-like evolution' of Tconset and a maximum at 146 GPa, but the evidence for the descending side above 146 GPa is limited to two samples (S#2 to 165 GPa, S#3 to 210 GPa) using only the 99.5% onset criterion. The difference between Tc99.5%R and Tc2-line at 146 GPa is already 10 K, and if the transition continues to broaden with pressure, the onset criterion may systematically overestimate the bulk Tc on the descending side. A quantitative analysis of Tcm, Tc2-line, or the resistance-drop magnitude as a function of pressure for all three samples is needed to distinguish a genuine dome from an onset-shift artifact. Without this, the 'dome-like' behavior is not established beyond a qualitative statement.","section":"§3 and Fig. 5"},{"comment":"No error bars are provided for either pressure or Tconset, and the measurement uncertainties are not discussed. The three-sample reproducibility is claimed qualitatively, but the scatter between S#1, S#2, and S#3 at overlapping pressures is not quantified. Since the paper's phase diagram is the central result, the authors should include pressure and temperature uncertainties, or at least clearly state the precision of the resistance and Raman measurements, and show the data points with error bars in Fig. 5.","section":"Figs. 2 and 5; Methods"}],"minor_comments":[{"comment":"Typographical error: 'the the top of the sample' should read 'the top of the sample.'","section":"Methods, High-Pressure Electrical Resistance Measurements"},{"comment":"The caption says 'see solids' but does not explain what the solid symbols represent; please clarify the symbol definitions for ambient-pressure and 80 GPa data.","section":"Fig. 4 caption"},{"comment":"The terms 'onset,' 'Tconset,' 'Tc99.5%R,' and 'Tc2-line' are used somewhat interchangeably. Please define each clearly at first use and state which criterion is used for each data point in Fig. 5.","section":"Main text, transition definition"},{"comment":"Ref. 2 is an arXiv preprint (2026). If a published version now exists, it should be cited. Also, the comparison data for cuprates are taken from many sources; a table listing compound, pressure range, and Tc values would improve readability.","section":"References"}],"recommendation":"major_revision","confidential_remarks":"The paper addresses a timely and interesting question, and the authors have clearly made a substantial experimental effort. My main concern is evidentiary: the headline claim of superconductivity at 210 GPa is supported by a single 99.5%-onset resistance drop, with the strongest corroborating measurements (field suppression, derivative analysis) limited to lower pressures. This is not an obvious error, but it is a load-bearing gap that can likely be fixed by re-analyzing existing data or by adding a short discussion with quantified broadening and uncertainty. I recommend major revision rather than rejection, provided the authors can substantiate the 210 GPa point with bulk-sensitive diagnostics or clearly qualify the claim."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The genuinely new thing here is the pressure range and the dome: freestanding La0.8Sr0.2NiO2 membranes measured up to 210 GPa, with Tconset peaking at 74.5 K near 146 GPa and then declining to 57.4 K at 210 GPa. The prior Nd-based membrane study stopped at 91 GPa without saturation, so this is a real step forward. The result is also reproducible across three samples in the overlapping pressure range, and the field-suppression data at 80 GPa plus the derivative/midpoint analysis in Fig. 3 give decent support to the claim that the resistance drop is superconducting and not just a broadening artifact. I think the reader's score of 6 for soundness is about right. The stress-test note is correct that the 210 GPa point rests on a single sample with no zero-resistance state and no field check at that pressure, and silicone oil is certainly not hydrostatic at 210 GPa. But that is the usual coin of the realm in ultrahigh-pressure transport; the field routinely uses 99.5% onset in diamond anvil work, and the three-sample consistency plus the Tcm trend mitigate the worry considerably. The bigger omission is experimental: no error bars for pressure or Tconset, no raw data in the supplement, and no explicit discussion of how the Raman pressure corresponds to the local pressure on the membrane. These are fixable with standard commentary and should not block refereeing. I would not call the persistence claim demonstrated as strongly as the title implies, but it is a reasonable working conclusion. The citation pattern looks fine; the comparison with cuprates and bilayer nickelates is contextual and not used as a load-bearing argument. This is a paper for the nickelate and high-pressure superconductivity crowd. It deserves a serious referee, probably with a request for error bars and hydrostaticity discussion, but it is not a desk reject. I would bring it to a reading group and likely cite it once the proper version appears.","headline":"A solid high-pressure transport study that extends nickelate Tc studies to 210 GPa and finds a dome; the top-pressure point rests on a single-sample onset, but the overall evidence is strong enough to referee.","tokens_in":11745,"tokens_out":1221,"would_cite":true,"duration_ms":13071,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["74.62.Fj","74.25.Dw","74.78.-w"],"model":"deepseek-v4-flash","headline":"Superconductivity in a freestanding La0.8Sr0.2NiO2 membrane survives compression to 210 GPa, with the onset temperature rising to 74.5 K near 146 GPa and easing to 57.4 K at 210 GPa.","keywords":["infinite-layer nickelate","superconductivity","high pressure","freestanding membrane","La0.8Sr0.2NiO2","diamond anvil cell","Tc dome","unconventional superconductivity"],"falsifier":"Measure the full R(T) curve to zero resistance, or an inductive/AC susceptibility signal, in a La0.8Sr0.2NiO2 membrane at about 150 and 210 GPa using a more hydrostatic medium such as cryogenically loaded helium or neon. If the resistance drop at 210 GPa does not reach zero, does not shift systematically with magnetic field, or is absent in a second pressure medium, the claim of superconductivity persisting to 210 GPa would be seriously undermined.","tokens_in":10782,"feed_emoji":"⚡","tokens_out":4354,"duration_ms":37885,"temperature":0.7,"pith_summary":"The authors set out to answer whether an infinite-layer nickelate superconductor can survive pressures beyond 100 GPa, where substrate-bound films cannot be measured. They measured electrical resistance of freestanding La0.8Sr0.2NiO2 membranes squeezed in diamond anvil cells up to 210 GPa. They report a continuous dome-shaped pressure dependence of the superconducting transition onset: from about 16 K at ambient pressure to a maximum of 74.5 K at 146 GPa, then a gradual decline to 57.4 K at 210 GPa. If correct, this is the first oxide superconductor shown to remain superconducting above 200 GPa, a robustness that contrasts with cuprates and bismuthates, where superconductivity is suppressed below roughly 40 GPa.","feed_headline":"Nickelate membrane stays superconducting to 210 GPa","feed_subtitle":"Onset Tc peaks at 74.5 K near 146 GPa, then falls gently—pressure endurance unseen in oxide superconductors.","key_machinery":"The central technical enabler is the freestanding infinite-layer nickelate membrane: a thin single-crystal La0.8Sr0.2NiO2 layer chemically released from its growth substrate and transferred onto the flat culet of a diamond anvil, with gold electrodes patterned on top. Resistance is measured in situ under pressure, with silicone oil as the pressure medium and pressure gauged by diamond Raman spectroscopy. The load-bearing analysis device is the definition of Tconset at a 99.5% resistance drop, cross-checked by the two-line intersection method and by the maximum of dR(T)/dT (Tcm), which separates real Tc enhancement from transition broadening.","core_discovery":"In freestanding, single-crystal La0.8Sr0.2NiO2 membranes transferred onto diamond culet surfaces, superconductivity—identified by a resistance drop with an onset Tconset defined at 99.5% of normal resistance—persists over an exceptionally wide pressure range. Three samples measured in diamond anvil cells give a consistent pressure–Tconset phase diagram: Tconset climbs nearly linearly below 60 GPa (slope 0.62 K/GPa), reaches about 74.5 K at 146 GPa, then slowly falls to 57.4 K at 210 GPa. The authors argue the rise is genuine because the midpoint temperature Tcm from dR/dT also increases fourfold with pressure, and the observed broadening of the transition is too small to explain the Tconset","pith_inferences":["Editorial inference: The reported persistence to 210 GPa raises the question whether other rare-earth-doped or stoichiometric infinite-layer nickelates could show even higher Tc if compressed beyond their current pressure limits; the paper does not test this.","Editorial inference: Because only the resistance-drop onset is reported at the highest pressures and the medium is solidified silicone oil, a direct check of zero resistance, Meissner or AC susceptibility, or at least a full resistive transition would strengthen the interpretation that bulk superconductivity, not a filamentary or contact artefact, persists at 210 GPa.","Testable extension: If the dome shape is intrinsic, one might expect a pressure-driven crossover or competing order near 146 GPa; future high-pressure structural and spectroscopic studies could look for a lattice or electronic anomaly there."],"forward_implications":["If the central claim is correct, superconductivity in this nickelate family persists across a 0–210 GPa window, implying the pairing mechanism does not require a delicate lattice or electronic state that pressure destroys.","The dome with a maximum near 146 GPa indicates that further compression beyond about 150 GPa does not help Tc; optimal conditions for this doping and composition sit near 146 GPa.","The similar peak Tc around 75 K in both La0.8Sr0.2NiO2 and Nd0.85Sr0.15NiO2 membranes, despite different rare-earth ions and different peak pressures, points to the NiO2 planes as the essential superconducting layer.","Pressure behavior differentiates infinite-layer nickelates from cuprates and Ba1-xKxBiO3, where superconductivity is killed at 18–39 GPa, suggesting a different pressure sensitivity of the superconducting phase.","The 0.62 K/GPa low-pressure slope and the subsequent nonlinear rise offer a quantitative target for theoretical models of nickelate superconductivity."],"fun_headline_variants":["Nickelate film superconducts to 210 GPa, peak 74.5 K","Record pressure endurance for oxide superconductor","Freestanding nickelate stays superconducting to 210 GPa","Tc peaks at 74.5 K under 146 GPa in nickelate membrane","Nickelate superconductor holds up to 210 GPa pressure"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The high-pressure resistance drop is assumed to be intrinsic superconductivity of the membrane, but at 146–210 GPa only the onset of the drop is measured on a membrane in solidified silicone oil, so pressure gradients, microcracks, or electrode-contact changes could in principle mimic or distort the signal.","fun_headline_variants_meta":{"raw":{"variants":["Nickelate film superconducts to 210 GPa, peak 74.5 K","Record pressure endurance for oxide superconductor","Freestanding nickelate stays superconducting to 210 GPa","Tc peaks at 74.5 K under 146 GPa in nickelate membrane","Nickelate superconductor holds up to 210 GPa pressure"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000783,"raw_usage":{"total_tokens":3304,"prompt_tokens":765,"completion_tokens":2539,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":509,"completion_tokens_details":{"reasoning_tokens":2444}},"tokens_in":509,"tokens_out":2539,"duration_ms":17551,"temperature":1.0,"reasoning_tokens":2444,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-04T16:09:24.844869+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the full R(T) curve to zero resistance, or an inductive/AC susceptibility signal, in a La0.8Sr0.2NiO2 membrane at about 150 and 210 GPa using a more hydrostatic medium such as cryogenically loaded helium or neon. If the resistance drop at 210 GPa does not reach zero, does not shift systematically with magnetic field, or is absent in a second pressure medium, the claim of superconductivity persisting to 210 GPa would be seriously undermined.","supporting_citations":[],"review_version":1}