{"id":"a44c916b-400f-4640-8f00-1e884adc0f8e","arxiv_id":"2607.04802","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"Altermagnetic CrSb and MnTe host locally chiral phonons with f-wave texture that couple to momentum-dependent spin-split bands; substitution unlocks net valley phonon chirality.","lead":"First-principles calculations show that altermagnets CrSb and MnTe host locally chiral phonons with an f-wave momentum texture, originating on the nonmagnetic sublattice. Chemical substitution can unlock net valley phonon chirality, and frozen-phonon distortions modify the spin-split electronic bands in ways photoemission might detect.","discovery_kind":"new_application","skeptic_critique":{"model":"grok-4.5","headline":"Frozen-phonon gaps do not isolate the chiral component of the mode, so the claimed chiral-phonon–spin-split-band coupling remains unseparated from ordinary lattice distortion.","rationale":"The Reader correctly isolates the weakest link: the frozen-phonon evidence does not separate the chiral contribution from the collective lattice distortion. That separation is load-bearing for the paper’s central claim of “chiral phonons coupled to spin-split bands.” All other reported results (local circular polarization on Sb/Te, f-wave texture, inversion-enforced cancellation, substitution-induced valley chirality) are internally consistent and do not require the same isolation. Because the paper itself flags the mixed character of the eigenvector, the concern is not an external imposition; it is an unclosed gap in the authors’ own argument. A single pair of controlled frozen-phonon calculations would settle the issue. Until that is done the contribution remains accept-shaped but conditional on clarifying the chiral channel—exactly the Reader’s CONDITIONAL verdict. No stronger objection (internal contradiction, numerical instability, or misidentification of altermagnetism) is present.","tokens_in":10104,"tokens_out":594,"duration_ms":5051,"concrete_test":"Recompute the unfolded bands of Fig. 4 with two controlled displacements of identical total amplitude: (i) only the circular Sb components of the K-mode eigenvector (Cr atoms fixed), and (ii) only the linear Cr components (Sb atoms fixed). If the ~0.1 eV gaps and momentum-selective repulsions appear exclusively (or predominantly) in (i), the chiral-coupling claim is supported; if they appear equally or more strongly in (ii), the claim that chirality itself drives the electronic modification is not established.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The paper’s strongest claim is that chiral phonons couple to momentum-dependent spin-split bands, producing characteristic electronic modifications (~0.1 eV gaps at half zero-point amplitude) accessible by photoemission. The only evidence offered is a frozen-phonon supercell calculation (Fig. 4) that displaces atoms according to the full eigenvector of the first nondegenerate optical mode at K. Immediately after that figure the authors state that the distortion mixes circular in-plane Sb motion with linear Cr displacements and that “the electronic response therefore arises from a collective structural modification rather than purely from the chiral component alone.” No control calculation is performed that freezes only the circular (chiral) part of the eigenvector while holding the linear Cr component at zero (or vice versa). Consequently the reported gaps and band repulsions cannot be attributed specifically to phonon chirality; they are consistent with any finite lattice distortion of comparable amplitude. The subsequent assertion of “momentum-dependent electron–phonon interaction” and experimental accessibility therefore rests on an untested identification of the chiral channel.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript uses DFT and finite-difference phonons to argue that the altermagnets CrSb and MnTe host locally chiral optical modes at the K/K' valleys, with phonon circular polarization (Eqs. 1–6) localized on the Sb/Te sublattice and an f-wave texture in the kz=0 plane. Inversion symmetry cancels the net valley phonon angular momentum in the pristine cells; isoelectronic substitution (Cr2AsSb, Mn2TeSe) is shown to lift that cancellation while preserving momentum-dependent spin splitting. The central claim is that these chiral modes couple to the altermagnetic spin-split bands, producing ~0.1 eV gaps and band repulsions under frozen-phonon supercell distortions (Fig. 4) that should be accessible to photoemission and related spectroscopies.","tokens_in":10329,"tokens_out":1311,"duration_ms":13118,"significance":"The coexistence of valley-chiral lattice dynamics and g-wave altermagnetic spin splitting on distinct sublattices is a timely and largely unexplored combination. If the local f-wave phonon textures, the substitution-induced valley contrast, and a genuine chiral channel in the electron–phonon coupling are robust, the work would open a concrete materials platform for chiral phononics without net magnetization and would motivate targeted ARPES/Raman experiments on CrSb and MnTe. Strengths include standard, reproducible DFT practice, an established Sz operator for phonon circular polarization, and explicit acknowledgment that pristine net valley chirality vanishes by symmetry. The substitution route and the surface-symmetry-breaking suggestion are useful, falsifiable control ideas.","major_comments":[{"comment":"Fig. 4 and the paragraph immediately following it: the central claim that “chiral phonons couple to momentum-dependent spin-split electronic bands” rests on a single frozen-phonon supercell distortion taken from the full K-valley eigenvector. The text itself states that the distortion mixes circular Sb motion with linear Cr displacements and that “the electronic response therefore arises from a collective structural modification rather than purely from the chiral component alone.” No control is reported that freezes only the circular (chiral) part of the eigenvector while holding the linear Cr component at zero (or the reverse). Without that separation, the reported ~0.1 eV gaps cannot be attributed specifically to phonon chirality and are consistent with any finite lattice distortion of comparable amplitude. A control calculation, or a clear downgrade of the claim to “phonon-mode-induce","section":"Fig. 4 and following paragraph"},{"comment":"Abstract and “Chiral phonon-electron coupling” section: the language “momentum-dependent electron–phonon interaction” and “possibly accessible by photoemission” is stronger than the calculation performed. Only static frozen-phonon band unfolding is shown; no electron–phonon matrix elements, spectral functions, or linewidth renormalizations are computed. Either compute at least a representative set of |g| or self-energy signatures that isolate the chiral mode, or rephrase to make clear that the evidence is limited to static band modifications under a mixed eigenvector displacement.","section":"Abstract; Chiral phonon-electron coupling section"},{"comment":"Eqs. (7)–(8) and Fig. 4(b): the zero-point length l_eff_0 ≈ 0.04 Å is used to argue physical relevance of the gaps, but the displacement amplitude remains a free parameter of the frozen-phonon protocol. The linear gap-vs-amplitude fit is expected for any first-order lattice modulation and does not by itself establish a chiral selection rule. Clarifying how the amplitude is chosen relative to the actual mode eigenvector normalization, and whether anharmonic or multi-mode effects would alter the gaps, would strengthen the experimental claim.","section":"Eqs. (7)–(8); Fig. 4(b)"}],"minor_comments":[{"comment":"Fig. 1 caption and main text: the path in the inset of Fig. 1 is described only as a “dashed line”; labeling high-symmetry points on the path would help readers connect the spin-split bands to the later K/K' phonon discussion.","section":"Fig. 1"},{"comment":"Fig. 3(c,d): the f-wave texture is visually clear, but a short quantitative multipole decomposition (or a statement of the angular Fourier component) would make the “six-lobes f-wave” assignment less qualitative.","section":"Fig. 3(c,d)"},{"comment":"The main text repeatedly refers to Supplemental Material for MnTe and for substituted compounds; a brief one-sentence summary of the MnTe phonon circular polarization in the main text would improve self-contained readability.","section":"Introduction / Local phonon circular polarization"},{"comment":"Typographical consistency: “anf-wave” appears without a space in the Introduction (“and anf-wave momentum-space texture”); fix to “an f-wave.”","section":"Introduction"},{"comment":"Reference [39] is used to support preservation of altermagnetism under substitution; a short statement of the magnetic moments or spin-splitting magnitude retained in the authors’ own Cr2AsSb/Mn2TeSe calculations would make that claim independent of the external reference.","section":"Doping-induced global chirality section; Fig. 5"}],"recommendation":"major_revision","confidential_remarks":"The local-chirality and substitution results look publishable and novel for this materials class. The overclaim on specifically chiral e–ph coupling is the main obstacle; if the authors either add a chiral-only control or tone the abstract/conclusions, the paper would be a solid contribution. Scope fits a materials-physics journal well. No concerns about circularity or fabricated entities."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"The new piece here is concrete: CrSb and MnTe host locally chiral optical modes at K/K' whose angular momentum lives on the Sb/Te sublattice and shows a six-lobe f-wave texture, while the g-wave spin splitting lives on Cr/Mn. Inversion cancels the net valley angular momentum; isoelectronic As/Se substitution lifts that cancellation without killing the altermagnetism. That sublattice separation and the substitution route are clean and useful.\n\nThey do the standard things well. Electronic bands match the known altermagnetic picture. Phonons come from finite differences; circular polarization is the usual Sz operator on the eigenvectors. Local sz maps and the f-wave pattern are internally consistent. Frozen-phonon supercells produce ~0.1 eV gaps already at half the zero-point amplitude, so the lattice really does rearrange the spin-split bands at physically relevant scales. Citations are appropriate and circularity is low.\n\nThe soft spot is exactly the one the stress-test flags, and the authors themselves flag it after Fig. 4: the frozen distortion mixes circular Sb motion with linear Cr motion, so the electronic response is collective, not proven to be the chiral component alone. No control that freezes only the circular part (or only the linear part) is shown. That weakens the strongest phrasing about “chiral phonons couple… through momentum-dependent electron–phonon interaction,” but it does not erase the local chirality results or the substitution-induced valley contrast. Experimental claims (ARPES, circular Raman) stay qualitative; no spectral functions or matrix elements. Main-text computational parameters are thin, but that is fixable.\n\nThis is for people already working on altermagnets or chiral phonons who want a materials platform and a clear next calculation (isolate the circular channel, surface breaking, actual e-ph matrix elements). It is not a conceptual revolution, but it is a real, reproducible materials result. I would send it to referees; they will ask for the control calculation and fuller methods, which is fair. Worth reading and, with those additions, worth citing.","headline":"Solid DFT mapping of local chiral phonons with f-wave texture in CrSb/MnTe and their sublattice separation from altermagnetism; the coupling claim is real but not yet isolated to the chiral part of the mode.","tokens_in":10985,"tokens_out":547,"would_cite":true,"duration_ms":4596,"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":"Altermagnets CrSb and MnTe host locally chiral phonons that couple to their spin-split bands and reshape the electronic structure.","keywords":["altermagnetism","chiral phonons","phonon angular momentum","electron-phonon coupling","CrSb","MnTe","valley phonons","spin splitting"],"falsifier":"An angle-resolved photoemission measurement on CrSb or MnTe (or a lightly substituted analogue) that either detects or rules out the predicted ~0.1 eV phonon-induced gaps and band-repulsion features at the spin-split crossings under resonant excitation of the chiral mode.","tokens_in":10956,"feed_emoji":"🔄","tokens_out":698,"duration_ms":5147,"temperature":0.7,"pith_summary":"Altermagnets combine zero net magnetization with momentum-dependent electronic spin splitting. This paper uses first-principles calculations to show that the prototypical compounds CrSb and MnTe also host locally chiral phonon modes: lattice vibrations that carry finite angular momentum with a six-lobe f-wave pattern in momentum space. The circular motion lives on the non-magnetic Sb or Te sublattice, while the spin splitting is generated by the magnetic Cr or Mn atoms, so the two phenomena arise from different parts of the same crystal. In the pristine crystals inversion symmetry cancels the net phonon angular momentum at each valley; isoelectronic substitution (As for Sb, Se for Te) lifts that cancellation and produces finite valley phonon chirality without destroying the altermagnetic order. Frozen-phonon distortions that follow these chiral eigenvectors open gaps of order 0.1 eV in the spin-split bands at amplitudes comparable to zero-point motion, indicating a direct electron–phonon channel that could be seen in photoemission. The work therefore presents altermagnets as materials in which spin, valley and lattice chirality can be addressed together.","feed_headline":"Altermagnets host chiral phonons that reshape spin-split bands","feed_subtitle":"Local circular lattice motion on Sb/Te couples to Cr/Mn spin splitting, opening ~0.1 eV gaps.","key_machinery":"Local phonon circular polarization (pseudospin) sz_α extracted from the phonon eigenvectors at the K/K′ valleys, whose momentum-space map yields the six-lobe f-wave texture and whose frozen-phonon supercell distortion is used to recompute the unfolded electronic bands.","core_discovery":"Prototypical altermagnets CrSb and MnTe support locally chiral phonon modes that carry finite phonon angular momentum with a six-lobe f-wave texture. These modes originate on the pnictogen/chalcogen sublattice and couple, via momentum-dependent electron–phonon interaction, to the spin-split electronic bands generated by the magnetic transition-metal atoms, producing characteristic modifications of the electronic structure that remain potentially detectable by photoemission.","pith_inferences":[],"forward_implications":[],"fun_headline_variants":["Chiral phonons from Sb/Te couple to spin-split bands in CrSb MnTe","Local f-wave chiral modes reshape altermagnetic spin splitting","CrSb MnTe host chiral phonons that modify spin-split electronic bands","Momentum-dependent e-ph coupling links chiral phonons to altermagnet bands","Six-lobe chiral phonon angular momentum couples to spin-split valleys"],"cache_read_input_tokens":128,"weakest_assumption_plain":"That the electronic-structure changes seen after displacing atoms along a mixed phonon eigenvector can be attributed specifically to the chiral component of that mode, rather than to the accompanying linear displacements of the magnetic atoms.","fun_headline_variants_meta":{"raw":{"variants":["Chiral phonons from Sb/Te couple to spin-split bands in CrSb MnTe","Local f-wave chiral modes reshape altermagnetic spin splitting","CrSb MnTe host chiral phonons that modify spin-split electronic bands","Momentum-dependent e-ph coupling links chiral phonons to altermagnet bands","Six-lobe chiral phonon angular momentum couples to spin-split valleys"]},"model":"grok-4.5","effort":"low","cost_usd":0.003894,"raw_usage":{"total_tokens":1257,"prompt_tokens":816,"num_sources_used":0,"completion_tokens":85,"cost_in_usd_ticks":38940000,"prompt_tokens_details":{"text_tokens":816,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":356,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":816,"tokens_out":85,"duration_ms":59465,"temperature":1.0,"reasoning_tokens":356,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-11T13:16:15.347671+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"An angle-resolved photoemission measurement on CrSb or MnTe (or a lightly substituted analogue) that either detects or rules out the predicted ~0.1 eV phonon-induced gaps and band-repulsion features at the spin-split crossings under resonant excitation of the chiral mode.","supporting_citations":[],"review_version":1}