{"id":"625c9d21-aa8b-4662-8302-25903760458c","arxiv_id":"2607.08553","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"Intercalating LaXO3 (X=Al,Ga,Sc) into La2NiO4 electron-dopes Ni planes disorder-free, putting La2NiO4:La2AlO4 at optimal filling for d-wave Tc exceeding 50 K.","lead":"Calculations show that stacking wide-gap LaXO3 layers into La2NiO4 donates electrons to Ni-3d orbitals without chemical disorder. This places La2NiO4:La2AlO4 at optimal filling for predicted d-wave superconductivity above 50 K and extends to La3Ni2O7.","discovery_kind":"new_method","skeptic_critique":{"model":"grok-4.5","headline":"Tc claim rests on a single-band Hubbard model whose U is hand-chosen and whose filling is taken from multi-orbital DMFT; residual multi-orbital and interface effects are not quantified.","rationale":"The Reader correctly isolates the single-band reduction plus hand-chosen U as the weakest link supporting the strongest claim. The doping mechanism (extra (LaO)+ layers transferring ~1 e- into Ni eg) is independently corroborated by DFT occupations, Bader/Mulliken charges, DOS, and DMFT, and the structural stability checks (SCPH, AIMD, convex hull) are solid. What remains untested is whether the quantitative Tc survives once the simplifications of Secs. IV–VIII are relaxed. Because the paper already flags multi-band pairing and interface effects as possible complications, the concern is internal rather than external. No stronger load-bearing flaw (e.g., dynamical instability or absence of charge transfer) appears. Hence the verdict stays CONDITIONAL; the concrete multi-orbital / dynamical-U recalculation would decide whether the Tc number can be trusted or must be demoted to a qualitative expectation.","tokens_in":21544,"tokens_out":640,"duration_ms":6057,"concrete_test":"Re-run the DΓA (or FLEX) calculation of λ SC(T) for the same hoppings but with (i) the frequency-dependent cRPA U(ω) instead of static U=6t and (ii) a two-orbital (dx2-y2 + dz2) model at the DMFT fillings of Table I; if the temperature at which λ SC=1 drops below ~40 K or the leading eigenvalue ceases to be pure d-wave, the “Tc exceeding 50 K” claim is no longer supported by the many-body methods used.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central quantitative claim (Tc exceeding 50 K, DΓA 53 K at n=0.87) is obtained only after projecting onto a single Ni-dx2-y2 band (Sec. IV), fixing the filling to the multi-orbital DMFT value n=0.87 (Table I), and setting U=6t=2.58 eV by hand because frequency-dependent cRPA U is omitted (Sec. IV). The multi-orbital DMFT spectra (Fig. 2c,d) still show residual La-5d pockets and a non-negligible dz2 occupation; the paper asserts these are “minor” but never recomputes the superconducting eigenvalue with a multi-orbital vertex or with the actual cRPA U. Interface reconstruction or broken inversion symmetry (explicitly flagged in the text) would further mix bands. Thus the numerical Tc is an extrapolation whose error bar is uncontrolled, even though the qualitative doping mechanism itself is robust.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript proposes a disorder-free electron-doping route for Ruddlesden–Popper nickelates by intercalating wide-gap LaXO3 (X=Al, Ga, Sc) blocks into La2NiO4 (and analogously La3Ni2O7). Extra (LaO)+ layers donate electrons into the NiO2 planes. DFT occupations, Bader/Mulliken charges, and multi-orbital DMFT spectra consistently show ~1 e− transfer, producing a near-half-filled Ni-dx2−y2 band (n≈0.87 in the La-5d+Ni-3d model) with nearly filled dz2. Structural stability is supported by SCPH phonons, AIMD, and a convex-hull analysis. Superconductivity is then estimated from a single-band Hubbard model (Wannier hoppings t′/t=−0.20, t″/t≈0.10, filling fixed to the multi-orbital DMFT value, U set to 6t) solved by DΓA, FLEX and DCA, yielding d-wave Tc values of ~53 K (DΓA), ~100 K (FLEX) and ~127 K (DCA).","tokens_in":21842,"tokens_out":1046,"duration_ms":9820,"significance":"Electron doping of nickelates has remained experimentally inaccessible by conventional A-site substitution; a clean, symmetry-preserving alternative would open the unexplored electron-doped side of the phase diagram and is therefore of high interest. The charge-transfer mechanism itself is robustly documented by multiple independent DFT and DMFT diagnostics and is shown to extend to the bilayer compound La3Ni2O7. The work also supplies concrete, falsifiable structural predictions (lattice constants, Ni–O bond lengths) and open data. The quantitative Tc claim, while secondary, is obtained with established many-body methods and places the proposed heterostructure in a regime previously identified as optimal for high-Tc d-wave pairing.","major_comments":[{"comment":"The central quantitative claim (Tc exceeding 50 K) rests on the single-band model of Sec. IV with U fixed by hand to 6t = 2.58 eV because the frequency-dependent cRPA interaction is omitted. Multi-orbital DMFT (Fig. 2c,d and Table I) still shows residual La-5d pockets and a non-zero dz2 occupation; the paper asserts these are “minor” but never recomputes the superconducting eigenvalue with a multi-orbital vertex or with the actual cRPA U. A controlled sensitivity study (or an explicit multi-orbital estimate) is needed to place an error bar on the reported DΓA/FLEX/DCA Tc values.","section":null},{"comment":"The text itself notes that inversion-symmetry breaking during growth “may introduce additional bands near the Fermi level \to multiband pairing.” Interface reconstruction and possible intermixing are not quantified. Because the doping mechanism relies on clean (LaO)+ donation, at least a model estimate of how modest interface disorder or polarity-driven reconstruction would alter the Ni filling and the single-band character is required before the “disorder-free” claim can be taken as experimentally robust.","section":null}],"minor_comments":[{"comment":"Table I lists both DFT and DMFT occupations; the caption and surrounding text should state more clearly which filling (0.87) is fed into the subsequent DΓA/FLEX/DCA calculations and why the La-pocket contribution is absorbed only as a rigid shift of n.","section":null},{"comment":"Fig. 4(a) uses a logarithmic fit λSC ≈ a − b ln(T) to extract Tc; the fitting window and the raw eigenvalue data should be shown or deposited so that the extrapolation can be reproduced.","section":null},{"comment":"The hoppings quoted in Sec. IV (t′/t = −0.20, t″/t = 0.10 or 0.11) differ slightly between the main text and the SM; a single consistent set should be used throughout.","section":null},{"comment":"Typographical inconsistencies appear in the abstract and introduction (“T c”, “d x2−y2”, missing spaces around colons in compound names). A uniform style for chemical formulas and orbital labels would improve readability.","section":null}],"recommendation":"major_revision","confidential_remarks":"The doping concept is novel and well supported; the Tc numbers are the weakest link and are presented more assertively in the abstract than the underlying approximations justify. If the authors can either (i) supply a multi-orbital or cRPA-U estimate of Tc or (ii) clearly relegate the numerical Tc to an order-of-magnitude illustration, the paper would be suitable for a high-profile condensed-matter journal. The open NOMAD data deposit is a genuine strength."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"The real news here is a practical, disorder-free way to electron-dope Ruddlesden-Popper nickelates: intercalate wide-gap LaXO3 (X=Al,Ga,Sc) so the extra (LaO)+ layers donate roughly one electron per Ni. DFT occupations, Bader/Mulliken, DOS, and multi-orbital DMFT all line up on ~3d9–δ with a near-half-filled dx2–y2 band for La2NiO4:La2AlO4, and they show the same charge transfer works for La3Ni2O7. Phonon/SCPH + AIMD + convex-hull checks give reasonable evidence the heterostructure is stable. That part is new relative to the substitutional and interface literature they cite, and it is immediately useful for thin-film groups.\n\nThey then project onto a single Ni-dx2–y2 Wannier band (t′/t = –0.20, t″/t ≈ 0.10), fix filling to the multi-orbital DMFT value n = 0.87, set U = 6t by hand because frequency-dependent cRPA is omitted, and run DΓA/FLEX/DCA. DΓA gives 53 K (higher at other fillings); FLEX and DCA give 100+ K. The hoppings sit in the “optimal” window of their earlier palladate/cuprate work, so the qualitative claim that the system sits near the sweet spot of the 2D Hubbard model is fair. The quantitative “Tc exceeding 50 K” is an extrapolation: residual La-5d pockets and dz2 weight are still visible in the multi-orbital spectra, inversion-symmetry breaking is flagged but not recomputed, and no multi-orbital vertex or actual cRPA U is used for the eigenvalue. The three methods also disagree by a factor of two. That soft spot is real but secondary; the doping mechanism itself does not rest on it.\n\nCitations and methods look solid (cRPA parameters from prior independent work, open NOMAD data). Self-citations are to established tools, not circular. This is for nickelate/cuprate theorists and MBE/PLD growers who want a concrete target. It deserves a serious referee; the central idea is clean enough that the community should see it even if the Tc number gets revised. I would engage.","headline":"Clean disorder-free electron-doping route for RP nickelates with solid DFT/DMFT evidence; the >50 K Tc is a one-band extrapolation whose error bar is uncontrolled.","tokens_in":22455,"tokens_out":606,"would_cite":true,"duration_ms":7034,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"Intercalating wide-gap LaXO3 layers into La2NiO4 donates electrons without disorder and places the nickelate in the optimal window for dx2-y2 superconductivity above 50 K.","keywords":["nickelate superconductors","electron doping","heterostructures","Ruddlesden-Popper","d-wave superconductivity","DMFT","first-principles"],"falsifier":"Grow epitaxial La2NiO4:La2AlO4 by molecular-beam epitaxy or pulsed-laser deposition, measure the Hall density and low-temperature resistivity; absence of electron doping near n ≈ 0.87 or of a superconducting transition above 50 K falsifies the central claim.","tokens_in":22447,"feed_emoji":"❄️","tokens_out":878,"duration_ms":19858,"temperature":0.7,"pith_summary":"Chemical substitution has never cleanly electron-doped Ruddlesden-Popper nickelates, leaving half the phase diagram unexplored. This paper shows that simply inserting insulating LaXO3 blocks (X = Al, Ga, Sc) into La2NiO4 creates extra (LaO)+ layers that transfer roughly one electron per nickel into the Ni-3d orbitals. The resulting La2NiO4:La2AlO4 heterostructure sits naturally near half-filling of the dx2-y2 band. Many-body calculations on that band then predict d-wave superconductivity with Tc exceeding 50 K even at ambient pressure. The same intercalation idea also electron-dopes the bilayer superconductor La3Ni2O7, giving a general, disorder-free design route for other layered oxides.","feed_headline":"Insulating layers electron-dope nickelates, predicting Tc over 50 K","feed_subtitle":"A clean intercalation route finally opens the missing electron-doped side of the phase diagram","key_machinery":"The extra (LaO)+ rocksalt layers introduced by LaXO3 intercalation transfer charge into the adjacent NiO2 planes without chemical disorder on the A or B sites.","core_discovery":"Intercalation of wide-band-gap LaXO3 layers into Ruddlesden-Popper nickelates supplies extra (LaO)+ units that act as clean electron donors, driving Ni toward a 3d9-δ configuration. For La2NiO4:La2AlO4 this places the dx2-y2 filling near the optimal value for high-Tc d-wave superconductivity, with DΓA, FLEX and DCA all predicting critical temperatures above 50 K.","pith_inferences":["Experimental realization of these superlattices would finally map the missing electron-doped half of the nickelate phase diagram.","Combining the charge-transfer doping demonstrated here with geometric quantum-well thickness control could open multigap or further elevated-Tc regimes.","The same intercalation strategy may solve long-standing electron-doping bottlenecks in manganites and cobaltates where tetravalent A-site substitution also fails."],"forward_implications":["La2NiO4:La2AlO4 is predicted to be an ambient-pressure d-wave superconductor with Tc > 50 K without any further chemical doping.","The same intercalation electron-dopes La3Ni2O7 and can be extended to other Ruddlesden-Popper oxides including cuprates and ruthenates.","Disorder-free doping should stabilize fragile correlated phases that conventional substitutional doping would disrupt.","The reduced in-plane lattice constant weakens correlations relative to infinite-layer nickelates and thereby raises Tc."],"fun_headline_variants":["Heterostructures unlock clean electron doping in nickelates","LaXO3 intercalation electron-dopes nickelates with Tc over 50 K","Insulating layers donate electrons to open nickelate phase diagram","Disorder-free doping puts La2NiO4 near optimal high-Tc filling","Extra LaO units drive nickelates to d-wave superconductivity above 50 K"],"cache_read_input_tokens":16512,"weakest_assumption_plain":"The predicted Tc rests on a single-band Hubbard model whose hoppings, filling and interaction are fixed by multi-orbital calculations and then treated as reliable inputs; if residual multi-orbital or interface effects matter, the high-Tc claim collapses.","fun_headline_variants_meta":{"raw":{"variants":["Heterostructures unlock clean electron doping in nickelates","LaXO3 intercalation electron-dopes nickelates with Tc over 50 K","Insulating layers donate electrons to open nickelate phase diagram","Disorder-free doping puts La2NiO4 near optimal high-Tc filling","Extra LaO units drive nickelates to d-wave superconductivity above 50 K"]},"model":"grok-4.5","effort":"low","cost_usd":0.005534,"raw_usage":{"total_tokens":1501,"prompt_tokens":772,"num_sources_used":0,"completion_tokens":84,"cost_in_usd_ticks":55340000,"prompt_tokens_details":{"text_tokens":772,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":645,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":772,"tokens_out":84,"duration_ms":6563,"temperature":1.0,"reasoning_tokens":645,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-10T05:28:45.301368+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"Grow epitaxial La2NiO4:La2AlO4 by molecular-beam epitaxy or pulsed-laser deposition, measure the Hall density and low-temperature resistivity; absence of electron doping near n ≈ 0.87 or of a superconducting transition above 50 K falsifies the central claim.","supporting_citations":[],"review_version":1}