{"id":"aaeca4ad-58fb-4525-be4a-1dcedeaa2a0b","arxiv_id":"2501.12647","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"Ambient-pressure tetragonal La4Ni3O10 shows no superconductivity or density-wave order up to 160 GPa, challenging the view that the tetragonal structure alone enables nickelate superconductivity.","lead":"We grew crystals of a nickelate material, La4Ni3O10, in a previously unavailable tetragonal form at ordinary pressure. They stay metallic and show neither superconductivity nor a density-wave transition even at 160 GPa, hinting that the density-wave order, not the crystal shape, may be what enables superconductivity in this family.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Powder XRD to only 27.7 GPa leaves the assumed I4/mmm stability to 160 GPa unverified; a high-pressure structural transition above 27.7 GPa would invalidate the central robust tetragonal metallic ground state claim.","rationale":"I read the paper as making two linked empirical claims: (i) the new ambient-pressure tetragonal crystals remain tetragonal and metallic up to 160 GPa, and (ii) no density-wave or superconducting transition appears in that range. The interpretation that the tetragonal structure is not necessary while the density-wave state is crucial is explicitly tentative and goes beyond the data, but even the empirical core (i) is under-supported because structural characterization stops at 27.7 GPa. The absence of a density-wave transition is well supported at ambient pressure by transport, torque, and repeated samples; the absence of superconductivity at high pressure is supported by transport on two tetragonal samples and by the observation that the same setup detects superconductivity in monoclinic controls. However, a negative transport result at extreme pressures without concurrent structural verification leaves open the possibility that the sample left the tetragonal phase. Since the monoclinic parent's superconductivity appears together with a transition to the tetragonal phase, the demonstration that a pre-formed tetragonal phase does not superconduct only has the claimed implication if the pre-formed phase is shown to remain tetragonal and to reach the same electronic state as the pressure-induced tetragonal phase. The reader's weakest-assumption analysis correctly identifies this gap; I agree. The proposed in-situ XRD test would directly settle it. I do not see a stronger concern: sample stoichiometry is a secondary uncertainty, and the paper makes a reasonable effort with SC-XRD refinement and iDPC imaging, but the extreme-pressure structure is the decisive unmeasured quantity.","tokens_in":12127,"tokens_out":5366,"duration_ms":54804,"concrete_test":"Perform in-situ synchrotron X-ray diffraction on the same batch of ambient-pressure tetragonal La4Ni3O10 microcrystals in a diamond-anvil cell up to at least 160 GPa, using the same pressure media (NaCl or Daphne oil 7373) and pressure calibration as the transport runs. Collect patterns at 300 K and at low temperatures, refine the lattice and space group, and compare with the high-pressure tetragonal phase of the monoclinic parent at overlapping pressures. If I4/mmm persists to 160 GPa and the lattice parameters and c-axis compressibility match the superconducting tetragonal phase over the relevant range, the structural concern is refuted; if a transition, peak broadening, or decomposition appears above 27.7 GPa, the central claim must be revised.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim that the ambient-pressure tetragonal phase of La4Ni3O10 hosts a robust tetragonal metallic state and no superconductivity up to 160 GPa requires that the I4/mmm structure, or at least the key electronic state, persists over the entire pressure range. The paper reports powder XRD only up to 27.7 GPa (Fig. 2f and Extended Data Fig. 4), and the high-pressure transport experiments on samples S3 and S4 are not accompanied by in-situ structural data or post-run recovery analysis. If a structural phase transition, lattice distortion, amorphization, or chemical reaction with the pressure medium occurs above 27.7 GPa, then the absence of superconductivity could reflect this new phase rather than the intrinsic electronic properties of the ambient-pressure tetragonal compound. This concern is especially load-bearing because the monoclinic parent becomes superconducting only in its high-pressure tetragonal phase; to conclude that the tetragonal structure is not necessary, one must show that the present crystals actually remain tetragonal and become electronically equivalent to that superconducting tetragonal phase at high pressure. The paper infers a Lifshitz transition around 20 GPa from resistance nonmonotonicity, but transport alone cannot rule out a structural origin for that behavior. Thus the 160 GPa negative result currently rests on an extrapolation of the structure beyond the measured range.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports the synthesis of ambient-pressure tetragonal (I4/mmm) La4Ni3O10 microcrystals using a high-oxidative-environment growth method and presents transport, magnetic torque, powder XRD, and DFT results. The key claims are that this tetragonal phase shows no density-wave transition at ambient pressure and no superconductivity up to 158.9 GPa, in contrast to the monoclinic phase which becomes superconducting after a pressure-induced structural transition to tetragonal. The authors interpret this as evidence that the tetragonal structure alone is not sufficient for superconductivity and that the density-wave order, or an associated electronic state, is crucial.","tokens_in":12310,"tokens_out":4154,"duration_ms":42583,"significance":"If correct, the paper provides a strong experimental constraint on theories of pressure-induced superconductivity in Ruddlesden-Popper nickelates: it suggests that the density-wave state is a necessary ingredient for superconductivity, rather than merely the tetragonal symmetry. The synthesis of an ambient-pressure tetragonal phase without octahedral tilting is an important materials achievement. The paper includes machine-accessible structural refinements, transport data to 158.9 GPa on two tetragonal samples, ambient-pressure magnetic torque, XRD to 27.7 GPa, and auxiliary DFT calculations; the central negative transport result is not dependent on fitted parameters. However, the structural persistence to the highest pressures, which underpins the interpretation of the negative result, is experimentally verified only to 27.7 GPa, leaving a significant gap.","major_comments":[{"comment":"The conclusion that the tetragonal I4/mmm structure persists up to 160 GPa is not supported by the data: powder XRD is reported only to 27.7 GPa, while the high-pressure transport on samples S3 and S4 extends to ~60 GPa and 158.9 GPa, respectively, with no in-situ structural confirmation. If a structural phase transition, amorphization, or chemical reaction occurs above 27.7 GPa, the absence of superconductivity could be due to a different crystal structure rather than the intrinsic electronic state of the ambient-pressure tetragonal phase. Since the paper's central interpretive claim (that the tetragonal structure is not necessary) rests on this structural equivalence, the authors should either provide structural data at higher pressures or explicitly qualify the conclusions as applying to the measured structural range.","section":"§2, Fig. 2f, Extended Data Fig. 4"},{"comment":"The DFT results reveal substantial differences between the ambient-pressure tetragonal (I4/mmm-AP) and high-pressure tetragonal (I4/mmm-HP) phases: the AP phase has additional dz2-derived Fermi pockets that disappear with pressure, indicating a Lifshitz transition. Yet the text in §2 describes the two tetragonal phases as 'almost identical.' This inconsistency matters because the argument that the tetragonal structure is not sufficient for superconductivity assumes that the AP tetragonal phase becomes electronically equivalent to the HP superconducting phase under pressure. The authors should reconcile these statements and discuss whether the differences in electronic structure might themselves explain the absence of superconductivity.","section":"§4, Fig. 4, §5 Discussion"},{"comment":"The manuscript acknowledges that precise oxygen content is difficult to determine and states that the oxygen content of the I4/mmm-AP phase is slightly larger than that of the P21/a-AP phase by ~0.04. While XRD refinement and iDPC imaging suggest near-stoichiometry, a small oxygen off-stoichiometry could in principle suppress superconductivity or alter the density-wave order. The negative result would be more convincing if the authors provided a more quantitative comparison of oxygen content between the tetragonal and monoclinic samples (e.g., via a direct measurement method) or a discussion of the known sensitivity of superconductivity to small oxygen vacancies in these nickelates.","section":"§5 Discussion and Methods"},{"comment":"The methods state that either NaCl or Daphne oil 7373 was used as the pressure-transmitting medium, but it is not specified which sample (S1–S4) used which medium. Non-hydrostatic or quasi-hydrostatic conditions can suppress superconductivity and may also influence structural transitions, so this information is essential for evaluating the negative results. Please specify the medium, pressure range, and any evidence for hydrostaticity for each sample.","section":"Methods: High pressure transport"}],"minor_comments":[{"comment":"The text reads 'the titled NiO6 octahedron' and 'a titled Ni-O-Ni bond'; this should be 'tilted' throughout.","section":"Introduction"},{"comment":"The phrase 'results with a moderalate R1 and wR2' contains a typo; it should say 'moderate R1 and wR2.'","section":"Methods: Structural characterization"},{"comment":"The figure caption states 'the two diffraction peaks can be well indexed by (107) and (110) for a tetragonal structural phase'; this is redundant, as 'tetragonal' already implies the structural phase, and the sentence could be shortened.","section":"Fig. 2g"},{"comment":"The abstract says 'orthogonal/monoclinic structure' for the parent nickelates; 'orthogonal' is an unconventional term for crystalline lattices, and 'orthorhombic' would be the standard descriptor for La3Ni2O7.","section":"Abstract"},{"comment":"The phase diagram is described as determined by data in Fig. 3a and 3b and Extended Data Fig. 7, but the structural boundary is taken from references [15,16]; this should be clearly indicated in the figure caption to avoid overstating the provenance of the structural transition line.","section":"§1, Fig. 1e"}],"recommendation":"major_revision","confidential_remarks":"The paper presents a valuable negative result with a novel synthesis, but the impact of the central interpretation hinges on the structural evolution of the ambient-pressure tetragonal phase under pressure. Given the paper's emphasis on the tetragonal symmetry as the key variable, the missing high-pressure structural data above 27.7 GPa is a substantive, fixable gap. The authors should either obtain higher-pressure XRD (which may be challenging but would directly address the concern) or clearly re-scope the conclusions to the measured structural range. If the latter, the paper would still be of interest but with a more modest claim."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Briefly, this is worth the community's attention. The group grew ambient-pressure tetragonal La4Ni3O10 microcrystals in flowing oxygen, solved the structure by SC-XRD and SAED, showed no density-wave anomaly in transport and torque at ambient pressure, and pushed resistance measurements on two tetragonal samples to about 159 GPa with no superconductivity and no density-wave signature. That is a new result: earlier tetragonal RP nickelates were oxygen-deficient and insulating, so this is the first near-stoichiometric tetragonal member, and the negative high-pressure transport is new. The DFT comparison, with the dz2 pockets in the ambient tetragonal phase, is auxiliary and clearly labelled.\n\nThe soft spots, in proportion. The main one is structural. Powder XRD is reported only to 27.7 GPa, and the claim of a robust tetragonal metallic ground state up to 160 GPa is an extrapolation. If the structure changes above 28 GPa - a distortion, amorphization, or reaction with the medium - then the absence of superconductivity would not be informative about the ambient tetragonal electronic state. The paper does not hide the data limit, but the abstract states the conclusion more strongly than the data allow. The Lifshitz transition inferred around 20 GPa from resistance nonmonotonicity could also have a structural origin; transport alone does not discriminate. Oxygen stoichiometry is a softer spot: the paper admits precise oxygen content is difficult, though iDPC imaging and site-occupancy refinement argue against large vacancies. That is a minor concern given the metallic transport, but not fully closed. I also want to flag that the central interpretive claim - density wave crucial, tetragonal structure not necessary - is a hypothesis, not a theorem. The discussion phrases it as a suggestion, which is fair, but the abstract edges toward a conclusion. The evidence is consistent, but the absence of both orders in one phase does not prove a causal link.\n\nOn the positive side, the paper is honest about its limitations. The citations are appropriate, the comparison with oxygen-deficient tetragonal phases is handled explicitly, and the synthesis and measurement protocols are described clearly enough to attempt reproduction. The structural refinement is careful.\n\nWho this is for: experimentalists and theorists working on nickelate superconductivity, particularly pressure synthesis and the role of octahedral tilting. It deserves a serious referee. My own view is conditional: I would accept it with a request to soften the structural claims, state the 27.7 GPa ceiling in the abstract, and add whatever post-run structural information exists. Read carefully, this is a solid negative result, not an overreach.","headline":"A clean negative result with a genuinely new material; the high-pressure structural gap above 27.7 GPa keeps the central interpretation from being fully sealed.","tokens_in":12980,"tokens_out":3089,"would_cite":true,"duration_ms":30042,"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":"Ambient-pressure tetragonal La4Ni3O10 never superconducts up to 160 GPa.","keywords":["nickelate superconductors","La4Ni3O10","Ruddlesden-Popper phases","density wave","high pressure","tetragonal structure","superconductivity","Fermi surface"],"falsifier":"High-pressure X-ray diffraction of the ambient-pressure tetragonal La4Ni3O10 above 27.7 GPa that reveals a structural phase transition would invalidate the conclusion, because the absence of superconductivity could then be attributed to a different crystal structure rather than to the intrinsic electronic state of the tetragonal phase.","tokens_in":11852,"feed_emoji":"🔬","tokens_out":4172,"duration_ms":38849,"temperature":0.7,"pith_summary":"This paper reports the first ambient-pressure tetragonal crystals of the trilayer nickelate La4Ni3O10, with flat, untilted NiO6 octahedra. Unlike the monoclinic ambient-pressure phase, which develops a density-wave transition near 135 K and becomes superconducting under pressure, the tetragonal crystals remain metallic down to 0.4 K and show no superconductivity up to 160 GPa. The authors argue that a tetragonal structure alone is therefore not enough to produce superconductivity in Ruddlesden–Popper nickelates; the density-wave state, or an electronic order tied to it, appears to be the essential ingredient. If correct, this narrows the search for ambient-pressure nickelate superconductors and constrains theories of the pairing mechanism.","feed_headline":"Tetragonal La4Ni3O10 stays metallic to 160 GPa, no superconductivity","feed_subtitle":"A new ambient-pressure tetragonal nickelate shows that lattice symmetry alone does not produce superconductivity.","key_machinery":"The central object is the ambient-pressure tetragonal phase of La4Ni3O10 (I4/mmm, no octahedral tilting), synthesized under flowing oxygen. The argument proceeds by comparing transport, magnetic torque, and DFT band structures across three phases: monoclinic P21/a at ambient pressure, tetragonal I4/mmm at high pressure (from prior work), and the new tetragonal I4/mmm at ambient pressure. The key comparison is that the monoclinic phase hosts a density-wave transition and becomes superconducting when pressurized into the tetragonal structure, whereas the ambient-pressure tetragonal phase, which never enters a density-wave state, also never superconducts. This decouples the tetragonal lattice symmetry from superconductivity and identifies the density-wave order as the variable that tracks the appearance of superconductivity.","core_discovery":"By growing La4Ni3O10 in a high-oxidative environment, the authors stabilize the I4/mmm tetragonal structure without octahedral tilting at ambient pressure, confirmed by single-crystal X-ray diffraction, electron diffraction, and powder X-ray diffraction up to 27.7 GPa. Transport and magnetic torque measurements show no density-wave transition in this tetragonal phase, and high-pressure resistance measurements up to 160 GPa find no superconductivity. In contrast, monoclinic La4Ni3O10 shows a density-wave transition near 135 K and superconductivity above about 20 GPa, with a structural transition to the tetragonal phase accompanying the onset of superconductivity. The simultaneous absence of both density-wave order and superconductivity in the ambient-pressure tetragonal phase leads the authors to conclude that the tetragonal structure is not sufficient for superconductivity and that the density-wave state is crucial. DFT calculations show that the ambient-pressure tetragonal phase has extra $d_{z^2}$-derived Fermi pockets that disappear under pressure, yet superconductivity is absent both with and without these pockets, arguing against a critical role for the $d_{z^2}$ orbital contribution.","pith_inferences":["If the density-wave order is the load-bearing ingredient, then a more direct route to ambient-pressure superconductivity in nickelates might be to stabilize a density-wave state at ambient pressure rather than merely achieving a tetragonal lattice.","The Lifshitz transition near 20 GPa in the tetragonal phase removes the extra $d_{z^2}$ pockets but does not restore superconductivity, suggesting the missing ingredient is the electronic correlations associated with the density wave, not the $d_{z^2}$ orbital character itself.","One testable extension is to synthesize an ambient-pressure tetragonal La3Ni2O7 and check whether it also lacks superconductivity under pressure; the paper's logic predicts it would, because no density-wave order would be present initially."],"forward_implications":["Tetragonal symmetry of the NiO6 octahedra is not sufficient for superconductivity in trilayer nickelates.","The density-wave state, or an electronic order tightly coupled to it, may be a necessary precursor for pressure-induced superconductivity in these materials.","The absence of superconductivity up to 160 GPa rules out simple structural arguments based solely on lattice symmetry and tilting angles.","The near-stoichiometric oxygen content, verified by diffraction refinement and electron microscopy, indicates that oxygen deficiency does not explain the absence of superconductivity."],"supporting_citations":[{"why":"Establishes the discovery of high-pressure superconductivity in La3Ni2O7 and the connection to the tetragonal structural transition.","marker":"[13]"},{"why":"Reports superconductivity in pressurized La4Ni3O10, providing the baseline for comparison.","marker":"[14]"},{"why":"Shows superconductivity in trilayer La4Ni3O10 single crystals with a structural transition to tetragonal.","marker":"[16]"},{"why":"Provides evidence of intertwined spin and charge density waves in La4Ni3O10 at ambient pressure.","marker":"[25]"},{"why":"Documents the pressure-induced structural transition to the tetragonal phase in La3Ni2O7, supporting the structural comparison.","marker":"[30]"},{"why":"Shows that high oxygen pressure growth conditions can stabilize higher-symmetry phases in R4Ni3O10, motivating the synthesis method.","marker":"[34]"},{"why":"Supplies the molten salt flux method used for crystal growth and the ambient-pressure monoclinic phase's resistivity behavior.","marker":"[35]"}],"fun_headline_variants":["Tetragonal La4Ni3O10: no superconductivity up to 160 GPa","Ambient-pressure tetragonal La4Ni3O10 lacks superconductivity","No density-wave, no superconductivity in tetragonal La4Ni3O10","Tetragonal La4Ni3O10 stays metallic to 160 GPa, no superconductivity"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The conclusion that the tetragonal phase itself lacks superconductivity depends on the premise that the ambient-pressure tetragonal structure remains the same I4/mmm phase up to 160 GPa, but powder X-ray diffraction was only measured up to 27.7 GPa.","fun_headline_variants_meta":{"raw":{"variants":["Tetragonal La4Ni3O10: no superconductivity up to 160 GPa","Ambient-pressure tetragonal La4Ni3O10 lacks superconductivity","No density-wave, no superconductivity in tetragonal La4Ni3O10","Tetragonal La4Ni3O10 stays metallic to 160 GPa, no superconductivity"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001109,"raw_usage":{"total_tokens":4727,"prompt_tokens":1153,"completion_tokens":3574,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":769,"completion_tokens_details":{"reasoning_tokens":3480}},"tokens_in":769,"tokens_out":3574,"duration_ms":25785,"temperature":1.0,"reasoning_tokens":3480,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-10T16:57:11.705734+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"High-pressure X-ray diffraction of the ambient-pressure tetragonal La4Ni3O10 above 27.7 GPa that reveals a structural phase transition would invalidate the conclusion, because the absence of superconductivity could then be attributed to a different crystal structure rather than to the intrinsic electronic state of the tetragonal phase.","supporting_citations":[],"review_version":1}