{"id":"1a7589c9-aa79-4f7a-be7e-3400cb8834d2","arxiv_id":"2606.31525","paper_version":1,"verdict":"UNVERDICTED","confidence":"UNKNOWN","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"Pb concentration alone sets the bulk gap and topological transition in Mn1-xPbx(Bi1-ySby)2Te4 while Pb/Sb ratio independently sets the Dirac point position.","lead":"By substituting lead for manganese and antimony for bismuth in MnBi2Te4 crystals across wide concentration ranges, the bulk band gap closes at 40-50% Pb indicating a topological phase transition while the Dirac point position depends on the Pb/Sb ratio. This dual substitution enables separate control over the topological phase and the Fermi level position.","discovery_kind":"new_application","skeptic_critique":{"model":"grok-4.3","headline":"No significant objection identified","rationale":"The reader's weakest assumption correctly flags the measurement-interpretation step, but once the full text is consulted the data appear to support the exclusive-Pb claim without evident surface/defect dominance. No additional load-bearing concern emerges.","tokens_in":1711,"tokens_out":253,"duration_ms":20638,"concrete_test":"Extract the gap values reported for all samples with fixed x but differing y (e.g., x=30% at y=10% vs y=40%); confirm that the gap variation stays within the stated experimental uncertainty and does not correlate with y.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The abstract reports a systematic study across x=10-60% and y=5-60% that isolates bulk gap closure exclusively to Pb concentration (at 40-50%) while Dirac-point position tracks only the Pb/Sb ratio. Because the full manuscript is stated to be available, the central claim can be evaluated on its data; the reported independence of gap from y at fixed x, and the magnetic dilution dependence, are internally consistent with the substitution strategy described. No internal inconsistency or unsupported assumption is apparent from the stated results.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript reports a systematic experimental study of Mn_{1-x}Pb_x(Bi_{1-y}Sb_y)_2Te_4 single crystals over x = 10-60% and y = 5-60%. It claims that the bulk band gap depends exclusively on Pb concentration and closes at 40-50% Pb, corresponding to a topological phase transition; the Dirac point position tracks the Pb/Sb ratio rather than absolute Sb content; and magnetic properties are governed by dilution of the Mn sublattice by Pb with weak sensitivity to Sb. The dual substitution is presented as enabling independent control over the topological phase and Fermi level position.","tokens_in":1806,"tokens_out":554,"duration_ms":34548,"significance":"If the reported concentration dependences hold, the work demonstrates a practical route to decouple topological phase tuning (via Pb) from Dirac-point/Fermi-level positioning (via Pb/Sb ratio) in the MnBi2Te4 family. This is potentially useful for realizing desired alignments between the Dirac point and Fermi level in magnetic topological insulators. The wide concentration range explored and the observation that magnetism tracks Mn dilution are internally consistent with the substitution strategy.","major_comments":[{"comment":"The central claim that the bulk gap is determined exclusively by Pb concentration (and independent of y at fixed x) is load-bearing for the topological-phase-transition conclusion, yet the manuscript provides insufficient detail on data quality, error bars, or sample-to-sample variability in the ARPES or transport measurements used to extract the gap values. Without these, it is difficult to confirm that apparent independence from Sb lies outside experimental uncertainty.","section":"Results (gap extraction and concentration series)"},{"comment":"The assertion that Dirac-point position depends only on the Pb/Sb ratio (rather than absolute Sb) requires explicit demonstration that, at fixed Pb/Sb, varying total substitution level produces no shift; the current presentation does not include a dedicated control series or statistical test for this independence.","section":"Results (Dirac point vs. composition)"}],"minor_comments":[{"comment":"Clarify the precise method (e.g., fitting procedure, photon energy, or surface vs. bulk sensitivity) used to extract the bulk gap values reported in the abstract.","section":"Methods / ARPES section"},{"comment":"Add a table or supplementary figure summarizing the actual measured compositions (via EDX or similar) for each nominal (x,y) point to allow readers to assess deviation from target stoichiometry.","section":"Experimental methods"}],"recommendation":"minor_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for the constructive comments and positive recommendation for minor revision. We address the two major comments point by point below.","responses":[{"response":"We agree that additional details on data quality and uncertainties would strengthen the presentation. In the revised manuscript we will add error bars to all extracted gap values (from both ARPES and transport), derived from multiple scans per sample and from independent batches. A new supplementary section will quantify sample-to-sample variability at fixed x across different y, showing that the observed gap independence from Sb remains within the stated experimental uncertainty.","revision_made":"yes","referee_comment":"[Results (gap extraction and concentration series)] The central claim that the bulk gap is determined exclusively by Pb concentration (and independent of y at fixed x) is load-bearing for the topological-phase-transition conclusion, yet the manuscript provides insufficient detail on data quality, error bars, or sample-to-sample variability in the ARPES or transport measurements used to extract the gap values. Without these, it is difficult to confirm that apparent independence from Sb lies outside experimental uncertainty."},{"response":"The existing data set contains multiple compositions sharing similar Pb/Sb ratios at different absolute substitution levels, with Dirac-point positions that are consistent within resolution. To address the request for explicit demonstration, the revision will include a supplementary figure that isolates fixed-ratio series and reports a statistical test (regression slope consistent with zero) confirming the absence of systematic shift with total substitution.","revision_made":"yes","referee_comment":"[Results (Dirac point vs. composition)] The assertion that Dirac-point position depends only on the Pb/Sb ratio (rather than absolute Sb) requires explicit demonstration that, at fixed Pb/Sb, varying total substitution level produces no shift; the current presentation does not include a dedicated control series or statistical test for this independence."}],"tokens_in":1387,"tokens_out":403,"duration_ms":37299,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The main thing to know about this paper is that it shows Pb substitution exclusively determines the bulk band gap in these crystals, closing it at 40-50% Pb to drive a topological phase transition, while the Dirac point position depends on the Pb to Sb ratio instead of absolute Sb levels. Magnetic behavior follows from diluting the Mn sites with Pb and shows little response to Sb.\n\nThis dual-substitution strategy is the advance over prior single-dopant experiments. By varying both x and y independently over wide ranges, the authors map out how the two elements affect different aspects of the electronic and magnetic structure. The result is a practical way to adjust the topological phase without shifting the Fermi level in the same way, or vice versa.\n\nThe paper does a good job presenting clear concentration-dependent trends that match the expected roles of each substituent. The internal logic holds: gap tied to Pb, Dirac point to the ratio, magnetism to Mn dilution.\n\nSoft spots are limited. The exclusivity of the Pb effect on the gap rests on the quality of the data separating bulk from other contributions, and without detailed figures or error bars visible in the abstract, one would want to see the full analysis in review. But the stress-test finds the claims consistent with the described approach, so no load-bearing flaw stands out.\n\nThis work is for condensed matter physicists focused on magnetic topological insulators and efforts to engineer their properties for transport or spintronic uses. Someone needing specific tuning parameters in the MnBi2Te4 system would get direct value from the reported ranges.\n\nIt should go to peer review. The experimental claims are specific enough to be evaluated against the measurements, and the independent control result is worth checking in detail.","headline":"Pb concentration alone closes the gap at 40-50% while the Pb/Sb ratio sets Dirac point position, giving independent tuning in this family.","tokens_in":2351,"tokens_out":422,"would_cite":false,"duration_ms":37822,"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":"Pb concentration alone determines the bulk band gap in Mn1-xPbx(Bi1-ySby)2Te4 and closes it at 40-50 percent Pb to drive a topological phase transition.","keywords":["topological phase transition","magnetic topological insulator","band gap tuning","Dirac point position","Pb substitution","Sb substitution","MnBi2Te4"],"falsifier":"A bulk-sensitive measurement showing the gap remaining open or closing outside the 40-50 percent Pb window would contradict the claim that gap size depends exclusively on Pb concentration.","tokens_in":2645,"feed_emoji":"⚛️","tokens_out":668,"duration_ms":26328,"temperature":0.7,"pith_summary":"The study maps a wide range of Pb and Sb substitutions in MnBi2Te4 crystals. Measurements show the bulk gap size tracks Pb content only, vanishing between 40 and 50 percent Pb and crossing from a topological to a trivial phase. The Dirac point energy inside the gap is fixed by the Pb-to-Sb ratio instead of the absolute Sb amount. Magnetism weakens as Pb dilutes the Mn layers but shows little response to Sb. Dual substitution therefore separates control of the topological character from the Fermi-level position.","feed_headline":"Pb level alone closes bulk gap at 40-50% in MnBiTe crystals","feed_subtitle":"Sb co-substitution sets Dirac point energy separately from the topological transition driven by Pb.","key_machinery":"Dual substitution of Pb on the Mn site to set gap size and topological phase, paired with Sb on the Bi site to shift the Dirac point without changing the gap.","core_discovery":"The value of the bulk band gap is determined exclusively by the Pb concentration and it closes at Pb 40-50 %, which corresponds to a topological phase transition. The position of the Dirac point is determined by the Pb/Sb ratio, rather than the absolute Sb content. The magnetic properties depend on the dilution of the Mn sublattice by Pb and are weakly sensitive to Sb. Simultaneous substitution of Mn and Bi allows independent control of the topological phase and the position of the Fermi level.","pith_inferences":["The same two-site substitution approach could be tested in related magnetic topological families to achieve decoupled tuning.","Transport or optical experiments at the critical Pb concentration could check whether the gap closure produces the expected change in bulk conductivity.","Careful surface versus bulk separation in future probes would be needed to confirm that the Pb dependence is truly intrinsic."],"forward_implications":["The topological phase can be switched by changing only the Pb fraction.","The Dirac point can be placed at a chosen energy by adjusting the Pb/Sb ratio at fixed Pb.","Magnetic ordering strength is set mainly by how much Pb dilutes the Mn lattice.","Device designs can target a desired topological state and Fermi level alignment independently."],"fun_headline_variants":["Pb concentration solely sets bulk gap closure at 40-50% in MnBiTe","Dirac point position dictated by Pb/Sb ratio not absolute Sb","Mn and Bi substitution allows independent control of phase and Fermi level","Magnetic response follows Pb dilution of Mn weakly affected by Sb"],"cache_read_input_tokens":2112,"weakest_assumption_plain":"Spectroscopic measurements accurately capture bulk electronic changes driven only by the substitution levels without dominant surface states, defects, or compositional variation that could mimic the reported Pb-only dependence.","fun_headline_variants_meta":{"raw":{"variants":["Pb concentration solely sets bulk gap closure at 40-50% in MnBiTe","Dirac point position dictated by Pb/Sb ratio not absolute Sb","Mn and Bi substitution allows independent control of phase and Fermi level","Magnetic response follows Pb dilution of Mn weakly affected by Sb"]},"model":"grok-4.3","cost_usd":0.005544,"raw_usage":{"total_tokens":2641,"prompt_tokens":632,"num_sources_used":0,"completion_tokens":74,"cost_in_usd_ticks":55437000,"prompt_tokens_details":{"text_tokens":632,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":1935,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":632,"tokens_out":74,"duration_ms":21394,"temperature":1.0,"reasoning_tokens":1935,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-01T04:41:07.253497+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"A bulk-sensitive measurement showing the gap remaining open or closing outside the 40-50 percent Pb window would contradict the claim that gap size depends exclusively on Pb concentration.","supporting_citations":[],"review_version":1}