{"id":"917da749-9af2-457c-b7ac-7a1e263ec747","arxiv_id":"2510.17522","paper_version":3,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"Rotating the Néel vector in monolayer Ta2TeSeO gaps one spin channel and leaves the other metallic, predicting an intrinsic antiferromagnetic half-metal.","lead":"This paper predicts that rotating the magnetic axis in a two-atom antiferromagnet, monolayer Ta2TeSeO, can leave one electron spin channel conducting while the other becomes insulating, with no net magnetization. If correct, this gives a low-power way to make spin-filtering devices from compensated antiferromagnets.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Half-metallic claim depends on unshown DFT values of δ1 and δ3 straddling EF; abstract and full text describe different mechanisms.","rationale":"The reader's weakest assumption correctly points to the DFT premise: Weyl cones at EF, δ shifts straddling EF, and near-degenerate in-plane easy axes. My stress-test concentrates on the most load-bearing subset of that premise: the manuscript does not actually show the values of δ1 and δ3, nor any spin-resolved Fermi-surface or DOS evidence, so the central half-metallic state is asserted rather than demonstrated. The symmetry argument itself is internally coherent—Eq. (1) for axial-vector mirrors, Eq. (4) for the Néel-vector-dependent mass, and Eq. (5) with independent δ_i are all standard—so I do not find a fatal flaw in the mechanism. The primary issue is evidentiary and presentational: the full text's title and introduction claim intrinsic half-metallicity, but the abstract and metadata describe a gapless DOS-driven filtering effect with transport polarization numbers that are never derived in the text. This is exactly the kind of mismatch that should be resolved before acceptance, but it is addressable by adding the missing numerical results and reconciling the two descriptions. Therefore I do not change the reader's CONDITIONAL verdict.","tokens_in":8659,"tokens_out":6964,"duration_ms":62162,"concrete_test":"Recompute the collinear SOC band structure of monolayer Ta2TeSeO with n∥x using the same functional and pseudopotentials as the paper. Identify the Weyl crossings along X–M1 and X–M3, extract δ1 and δ3 (crossing energies relative to EF) and the SOC gap in the opposite spin channel, and compute spin-resolved DOS at EF. If the two protected crossings are not on opposite sides of EF, or if the opposite spin channel has nonzero DOS at EF, the claimed intrinsic half-metal is not realized.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim in the v2 full text is an intrinsic AFM half-metal in monolayer Ta2TeSeO: for n∥x the two surviving Weyl cones in one spin sector are shifted in opposite energy directions so that this sector retains a Fermi surface at EF, while the other sector is gapped. This conclusion requires the DFT values of δ1 and δ3 (Eq. 5) to straddle EF and requires the mirrored-neighbor cone to be fully gapped. The manuscript provides none of the supporting numbers: no SOC band-structure figure, no extracted δ1, δ3, no gap magnitude for the gapped sector, no Fermi-surface plot, no spin-resolved DOS. The abstract's conductivity polarization (76.4–82.0% at 20 K) is attributed to a semiclassical transport calculation that does not appear in the full text. Moreover, the abstract in v1/metadata describes a gapless direction-robust filtering mechanism with 'no conventional spin-selective band gap,' while the full text's title and introduction claim a spin-selective gap and half-metallicity—these are different central claims. The symmetry logic (Eqs. 1–5) is internally coherent, and the argument that a unitary mirror forbids the σ_y mass is standard; the weak link is that inequivalence δ1≠δ3 alone does not guarantee half-metallicity. The protected cones must actually lie on opposite sides of EF in the converged DFT calculation. Without those numbers the central claim cannot be checked from the manuscript as written.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"This manuscript claims that monolayer Ta2TeSeO is a compensated altermagnetic Weyl semimetal whose magnetic space group can be reduced by rotating the Néel vector, converting it into an intrinsic AFM half-metal. The symmetry argument (Eqs. 1–4) is: for n∥x/y one unitary mirror survives, protecting single-spin Weyl cones; the orthogonal mirror becomes magnetic, permitting an SOC-induced mass term in the opposite spin sector; breaking unitary C2z (leaving only C2zT) allows the two surviving cones in the protected sector to shift relative in energy (Eq. 5, δ1≠δ3), giving one spin channel a Fermi surface. The abstract additionally reports 76.4–82.0% conductivity polarization at 20 K from semiclassical transport, while the full text presents the central result as an intrinsic AFM half-metal with a single-spin Fermi surface.","tokens_in":8910,"tokens_out":3540,"duration_ms":31929,"significance":"The symmetry mechanism is clean, parameter-free, and potentially general: it identifies a concrete set of design criteria (Weyl cones near EF, no horizontal mirror Mz, switchable in-plane Néel vector). If the quantitative half-metallic state is actually realized, this would be a notable conceptual advance in antiferromagnetic spintronics. The k·p treatment of the forbidden mσy mass under a unitary mirror is standard and internally coherent. The manuscript explicitly uses DFT for material parameters and provides no free parameters fitted to the target result; these are strengths. However, the decisive numerical support for the central half-metal claim is absent, so the significance is conditional on data the manuscript does not currently contain.","major_comments":[{"comment":"The central claim—half-metallicity for n∥x—rests on δ1≠δ3 straddling EF and on the opposite spin sector being fully gapped. The manuscript provides no SOC band-structure plot with an energy axis, no numerical values for δ1 and δ3, no gap magnitude for the gapped sector, and no spin-resolved Fermi surface or DOS. The phrase 'by small symmetry-compatible tuning (strain, gating)' indicates the effect may require additional tuning, but the nominal zero-strain state is not quantified. Without these numbers the half-metal claim cannot be checked from the manuscript as written.","section":"Eq. (5), Fig. 3(b)"},{"comment":"The abstract reports quantitative transport (76.4–82.0% at 20 K, full-Brillouin-zone Wannier interpolation, semiclassical transport) but the full text contains no transport calculation, no conductivity-polarization formula, and no current-direction analysis. The full text instead emphasizes an 'intrinsic AFM half-metal' with a 'single-spin Fermi surface,' whereas the abstract describes a 'gapless, direction-robust spin-filtering mechanism that requires neither a spin-selective band gap nor a large velocity contrast.' These are different central claims. The manuscript must be made internally consistent and must either present the transport calculation or remove/adjust the quantitative abstract claim.","section":"Abstract vs full text"},{"comment":"The mechanism requires symmetry-protected Weyl cones near EF in the SOC-free limit, and then a spin-selective gapping and energy shifting. The text states that theory predicts spin-polarized Weyl nodes pinned near the Fermi level and gives the Ta moment (~0.73 μB), but no SOC-free or SOC band-structure coordinates, node energies, or δ1, δ3 values are provided. If the nodes are not at EF, or if δ1 and δ3 do not straddle EF, the half-metallic state is not realized. Please provide the quantitative band structure and, ideally, the carrier density or DOS at EF for both spin channels.","section":"Fermi-level position and Weyl-node energies"}],"minor_comments":[{"comment":"The title contains a typo: 'Néel-V ector' should be 'Néel-Vector'.","section":"Title"},{"comment":"Fig. 3 is captioned as spin-projected band structures for different Néel-vector orientations, but no energy axis, node energies, or gap sizes are given. Adding these would also address the major quantitative concerns.","section":"Fig. 3"},{"comment":"The direction 'd≡(110)' should be written as [110] (or {110} when referring to a family). Also, the text alternates between 'C2z' and 'C2zT' without a compact magnetic-space-group notation; a table of the surviving symmetry generators for each n would improve clarity.","section":"Notation"},{"comment":"In Eq. (4), the proportionality m(n)∝λ|n⊥| is claimed but not derived in detail. A brief derivation or a sentence clarifying that n⊥ is the component of n perpendicular to the mirror plane would help the reader.","section":"Eq. (4)"}],"recommendation":"major_revision","confidential_remarks":"The manuscript reads like a compact extended abstract from which quantitative transport results were removed, while the abstract still advertises them. The symmetry logic is sound and the topic is timely, but the central half-metal claim is currently unsupported by the data in the full text. This is fixable within the manuscript's scope by adding the missing DFT/SOC band-structure numbers, gap magnitudes, and (if kept) the transport calculation. If those numbers do not confirm the claimed straddling of EF, the conclusion would need to be weakened accordingly."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The genuinely new thing here is the mechanism: rotating the Néel vector in a 2D altermagnet first turns one unitary mirror into a magnetic mirror, allowing a SOC mass in one spin sector, then breaking C2z lifts the energy equivalence of the surviving Weyl cones so one spin sector keeps a Fermi surface while the other gaps. That is a real conceptual step beyond the transport analogues and strain-driven half-semimetals cited in the paper. The symmetry logic itself is standard and coherent: Eq. (1) correctly handles axial-vector mirror transformations, Eq. (3) reflects the known mirror-forbidden sigma_y mass, and Eq. (5) is a reasonable k·p minimal model. The claim that a unitary mirror forbids the mass while an antiunitary one does not is correct, and the paper states the required conditions (M_z broken, Weyl cones near E_F, nearly degenerate in-plane anisotropy) explicitly. The authors also give a concrete material candidate, Ta2TeSeO, with calculated exchange parameters and a Néel temperature estimate in the SM.\n\nThe soft spots are real but mostly about presentation and missing numbers. The abstract and v1 metadata describe a gapless direction-robust filtering mechanism with 76.4–82.0% conductivity polarization at 20 K, while the v2 full text claims an intrinsic half-metal and contains no transport calculation at all. The title changed too. That is not a fatal flaw if the authors reconcile the versions, but as it stands the reader cannot tell which claim is being made. More importantly, the central half-metallic claim depends on the DFT values of delta_1 and delta_3 straddling E_F so that one cone is occupied and the other empty in the protected spin sector. The paper does not show those numbers: no SOC band-structure figure with spin projection, no extracted delta_1 and delta_3, no gap magnitude for the gapped sector, no Fermi-surface plot. The stress-test note worries about exactly this, and I think the concern lands. The symmetry argument permits the half-metal; it does not by itself prove the DFT realization. The claim that the two surviving cones are pushed to opposite sides of E_F is a quantitative assertion and needs the numbers.\n\nThe citation pattern looks fine. The paper distinguishes its result from prior work, and the SM existence is mentioned but not provided in the v2 text I have—that is a practical issue for referees.\n\nNet: this is a serious paper with a plausible and possibly important mechanism, but the version inconsistency and missing quantitative evidence make it impossible to verify the central claim from the manuscript alone. I would send it to peer review: a good referee can force the authors to (a) merge the two versions, (b) provide the SOC band structure with spin-resolved Weyl cone positions and delta_1/delta_3 values, and (c) either add the transport calculation or remove the abstract's conductivity numbers. The symmetry analysis alone may be publishable even if the half-metal realization fails for this specific material, but the paper as written needs the numbers.","headline":"A clear symmetry argument for a possible AFM half-metal, but the version mismatch and missing quantitative DFT results keep it from being checkable as submitted.","tokens_in":9491,"tokens_out":725,"would_cite":true,"duration_ms":8735,"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":"The paper claims that reorienting the Néel vector in the compensated two-dimensional altermagnet Ta2TeSeO converts it into an intrinsic antiferromagnetic half-metal—one spin channel metallic, the other gapped—at zero net magnetization.","keywords":["altermagnetism","antiferromagnetic half-metal","Weyl semimetal","Néel vector","magnetic space group","spin filtering","2D magnets","Ta2TeSeO"],"falsifier":"A spin-resolved DFT band-structure calculation of Ta2TeSeO with the Néel vector along x that finds Fermi-level crossings in both spin channels, or finds both surviving Weyl cones on the same side of the Fermi level, would falsify the half-metallic claim; likewise, a computed in-plane easy-axis anisotropy large enough to prevent Néel reorientation below reasonable fields would remove the switching premise.","tokens_in":8475,"feed_emoji":"🧲","tokens_out":5021,"duration_ms":44853,"temperature":0.7,"pith_summary":"The paper tries to establish that a compensated antiferromagnet can become a genuine half-metal—one spin channel metallic, the other gapped—without any net magnetization, simply by reorienting the Néel vector. In monolayer Ta2TeSeO, an altermagnetic Weyl semimetal with two spin-polarized Weyl-cone pairs pinned near the Fermi level, aligning the magnetic axis along the in-plane x or y direction breaks exactly the right mirror and rotation symmetries: one spin sector stays gapless while the other acquires a spin-orbit mass gap, and the surviving cones shift apart in energy so that only one spin channel retains a Fermi surface. The predicted longitudinal conductivity polarization is between 76.4% and 82.0% for every in-plane current direction at 20 K, with zero net moment. Because the in-plane anisotropy is nearly degenerate, weak strain or weak magnetic fields can reversibly switch which spin channel conducts, and the symmetry recipe is offered as a general design principle for other two-dimensional Lieb-lattice altermagnets.","feed_headline":"One Néel-vector rotation creates an antiferromagnetic half-metal","feed_subtitle":"In monolayer Ta2TeSeO, aligning the magnetic axis in plane leaves a single spin channel metallic at zero net moment.","key_machinery":"The central mechanism is Néel-vector-oriented magnetic space-group reduction. Because a magnetic moment is an axial vector, a mirror reflection Mx acts as (Sx, Sy, Sz) → (Sx, −Sy, −Sz): fixing the Néel vector along x preserves Mx as a unitary symmetry but makes My magnetic (MyT), and forces C2z to pair with time reversal, leaving only C2zT. This determines whether the k·p mass term m σy, odd under the surviving mirror, is symmetry-forbidden in one spin sector (keeping it gapless) or symmetry-allowed in the other (gapping it), while the loss of unitary C2z permits independent energy shifts δ1 and δ3 of the two remaining Weyl cones, driving the semimetal-to-half-metal transition.","core_discovery":"Fixing the Néel vector along x (or y) converts Ta2TeSeO from a compensated altermagnetic Weyl semimetal into an intrinsic antiferromagnetic half-metal. The unitary mirror Mx survives and protects the Weyl crossings in one spin sector, while the orthogonal mirror becomes a magnetic mirror, allowing a spin-orbit-induced mass term to open a gap only in the opposite sector. Simultaneously, breaking the unitary C2z symmetry, leaving only the antiunitary C2zT, lifts the energy equivalence of the two surviving mirror-pinned Weyl cones, so one cone moves above the Fermi level and the other below it. The result is a single-spin Fermi surface at zero net magnetization, a state the paper calls an intri","pith_inferences":["A testable extension: because the mechanism only requires a mirror-pinned spin-polarized Weyl pair near the Fermi level and no horizontal mirror, a high-throughput first-principles search over Janus-type Lieb-lattice altermagnets should find additional platforms beyond Ta2TeSeO.","The half-metallic state here is gapless in the conducting channel, so spin-polarized scanning tunneling spectroscopy or angle-resolved photoemission would be a cleaner direct test of the single-spin Fermi surface than bulk conductivity, which sees the 76–82% polarization.","The residual antiunitary C2zT symmetry protects the gaplessness of the conducting channel; perturbations that preserve it should leave the half-metallic state intact, while perturbations that break it would open a gap in the conducting sector, providing a robustness criterion for device design.","The near-degeneracy of the in-plane easy axes suggests a two-state spin selector controlled by an order parameter with no stray field; engineering this degeneracy with strain could make the switching low-power and fast, relevant for antiferromagnetic spintronic memory concepts."],"forward_implications":["With the Néel vector along x, the spin-up channel is metallic and the spin-down channel is gapped; along y, the same half-metallic state appears with the spin polarization reversed.","With the Néel vector along z, both spin sectors acquire equal gaps, giving a compensated insulating state; along the in-plane diagonal, both sectors host energy-inequivalent gapped cones.","The longitudinal conductivity polarization remains positive for every in-plane current direction at charge neutrality and 20 K, ranging from 76.4% to 82.0%, demonstrating direction-robust spin filtering without a conventional spin-selective band gap.","Because the in-plane magnetic anisotropy is nearly degenerate, minute strain, weak magnetic fields, or, the paper suggests, circularly polarized light can reversibly switch the conducting spin channel without generating a net moment.","The mechanism yields concrete design criteria—mirror-protected altermagnetic Weyl cones near the Fermi energy, absence of horizontal mirror symmetry, and a Néel direction that lowers the magnetic space-group symmetry—and is predicted to extend to other two-dimensional decorated Lieb altermagnets such as V2SeSO and Nb2SeTeO."],"fun_headline_variants":["Spin filtering that works for any current direction","Flipping a magnetic axis turns altermagnet into half-metal","A single rotation creates a gapless spin filter","Ta2TeSeO: a stable path to direction-robust spin currents","No gap? No problem: altermagnet spins filter every way"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The whole result rests on the DFT prediction that Ta2TeSeO is a compensated altermagnet with spin-polarized Weyl cones sitting right at the Fermi level and almost equal in-plane easy axes; if the cones are not at the Fermi level, or the symmetry-lowering shifts do not push one cone above and one below it, the half-metal is not realized.","fun_headline_variants_meta":{"raw":{"variants":["Spin filtering that works for any current direction","Flipping a magnetic axis turns altermagnet into half-metal","A single rotation creates a gapless spin filter","Ta2TeSeO: a stable path to direction-robust spin currents","No gap? No problem: altermagnet spins filter every way"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.00033,"raw_usage":{"total_tokens":1747,"prompt_tokens":887,"completion_tokens":860,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":631,"completion_tokens_details":{"reasoning_tokens":785}},"tokens_in":631,"tokens_out":860,"duration_ms":6953,"temperature":1.0,"reasoning_tokens":785,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-04T09:01:12.634566+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A spin-resolved DFT band-structure calculation of Ta2TeSeO with the Néel vector along x that finds Fermi-level crossings in both spin channels, or finds both surviving Weyl cones on the same side of the Fermi level, would falsify the half-metallic claim; likewise, a computed in-plane easy-axis anisotropy large enough to prevent Néel reorientation below reasonable fields would remove the switching premise.","supporting_citations":[],"review_version":1}