{"id":"c41ceb13-5b1f-4963-b3bd-99d87628a5df","arxiv_id":"2506.23598","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"SiTc is predicted to be a chiral crystal that simultaneously hosts multifold topological fermions and topological phonons with chiral Fermi arcs.","lead":"The authors used density functional theory to predict that the chiral crystal SiTc hosts both topological fermions (Weyl points, multifold crossings, Fermi arcs, spin Hall conductivity) and topological phonons with chiral surface arcs. A generalist should care because SiTc could become a single material platform for studying how electronic and vibrational topology interact, relevant for thermoelectrics and spintronics.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Phononic topological edge states rest on an unverified Wannier interpolation of 12-13 THz bands, with no quantitative gap or entanglement analysis; if those bands hybridize, the claimed chiral phonon Fermi arcs are not established.","rationale":"The reader's weakest_assumption precisely identifies the phononic band-selection issue, and I agree it is the most load-bearing unsecured step. The electronic part of the paper is standard and internally consistent: symmetry analysis, SOC-induced degeneracy splitting, Weyl node chirality counts that sum to zero, and surface-state/Fermi-arc calculations are all compatible with established methods. The phononic claim, by contrast, is the less-supported pillar of the paper's central 'simultaneous fermionic and bosonic topology' assertion, and it is the one most likely to be an artifact of the Wannier interpolation. The text explicitly says 'well separated bands' but supplies no gap values, no Wannier-band comparison, and no entanglement analysis; these omissions are exactly the checks that would distinguish a genuine topological phonon manifold from a numerical artifact. I also note the self-referential limitation: the full phonon dispersion in Figure 6(a) appears to show the 12-13 THz manifold approaching lower branches at some k-points, so the isolation assumption is not obviously satisfied. Because the verifiable electronic results are promising but the phononic topology is not yet established, CONDITIONAL is the correct verdict: the paper should be accepted only after the phononic interpolation is validated or the claim is softened. The 'longest Fermi arc' overstatement is a separate but related issue, and it should be either quantified against known chiral phonon systems or removed.","tokens_in":11264,"tokens_out":1628,"duration_ms":21445,"concrete_test":"Recompute the phonon topological invariants without relying on the selected-band Wannier Hamiltonian: (1) From the DFPT dynamical matrix on the full BZ, compute the minimum frequency gap between the 12-13 THz manifold and the next lower phonon branch at every k; if this gap closes or drops below, say, 0.1 THz at any point, the manifold is not isolated and the Wannier interpolation is unreliable. (2) Construct Wilson-loop Chern numbers for the three/four-band manifold directly from the raw DFPT eigenvectors on a dense k-mesh (e.g., 24x24x24) and compare with the PHONOPYTB-derived Chern numbers. (3) If the Chern numbers agree and the gap is nowhere small, the phononic Fermi arcs in Figure 7(b,e) survive; otherwise the claimed topological phononic edge states and the 'longest Fermi arc' are artifacts of the interpolation choice.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim that SiTc simultaneously hosts topological fermionic and bosonic excitations depends critically on the phononic edge-state result, which itself depends on the choice of the uppermost phonon bands (12-13 THz) as an isolated manifold. The paper states these bands are 'well separated' but provides no quantitative frequency gap to the next lower branch, no comparison between the DFPT phonon dispersion and the Wannier-interpolated (PHONOPYTB/WannierTools) bands, and no band-entanglement analysis. If the selected manifold hybridizes with lower optical branches anywhere in the BZ, the Wannier interpolation can produce incorrect Berry curvature, incorrect Chern numbers, and spurious surface Fermi arcs. The electronic counterpart is more secure because it uses standard MLWF procedures and the Weyl chirality counts sum to zero, but the phononic topology is the less-supported half of the paper's headline coexistence claim. Additionally, the 'longest possible Fermi arc' statement in the phononic section is presented without any comparison to other materials, so it is an overclaim even if the arc is real. A further internal inconsistency risk: the phonon Wannier interpolation implicitly assumes a gap-separated subspace, but the figure shows the 12-13 THz manifold touches other bands near Γ in the full dispersion; the zoomed views may hide that the selected bands are not spectrally isolated there. This directly threatens the bulk-surface correspondence used to interpret Figure 7.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript presents first-principles density functional theory and symmetry-based analyses of the chiral compound SiTc (space group 198). It reports electronic multifold nodes at Γ and R in the absence of spin-orbit coupling (three-fold and four-fold, respectively) and with spin-orbit coupling (four-fold and six-fold, respectively), Weyl points W1-W6 with chiralities that sum to zero, surface Fermi arcs, Berry curvature distributions, and computed spin Hall conductivity. On the phononic side, it reports three-fold and four-fold bosonic nodes at Γ and R in a selected 12-13 THz window and claims chiral surface phonon Fermi arcs connecting these nodes. The central claim is that SiTc simultaneously hosts topological fermionic and bosonic excitations, making it a candidate for exploring the interplay between electronic and phononic topology.","tokens_in":11566,"tokens_out":7664,"duration_ms":79258,"significance":"If fully substantiated, the coexistence of topological electronic and phononic excitations in a single synthesized chiral material would be of genuine interest for transport, thermoelectric, and possible device applications. The electronic analysis is carried out with standard methods (VASP, Wannier90, WannierTools), includes a check of the Nielsen-Ninomiya theorem, and provides explicit numerical values for spin Hall conductivity. The phononic part is novel but is the weaker half of the paper, because the topological assignment rests on an unquantified frequency window and an unvalidated Wannier interpolation. The manuscript would benefit from a focused revision that validates the phononic topology and resolves internal inconsistencies in the symmetry analysis.","major_comments":[{"comment":"The symmetry analysis contains a direct internal contradiction in the commutation relations used for the Γ point. In the first paragraph, the screw symmetries S2y and S2z are stated to commute, [S2y, S2z] = 0, with S2y^2 = I and S2z^2 = I, while the later paragraph on spin-orbit coupling states that \"The screw symmetries S2y and S2z anticommute and square to -I.\" Both statements are used to derive the allowed degeneracies at Γ. The authors must clarify that these relations depend on whether the spinless or spinful representation is being considered, and then provide a consistent derivation of the four-fold degeneracy in the presence of SOC. As written, the conflicting statements undermine the symmetry-protection argument that is central to the paper.","section":"Symmetry Analysis"},{"comment":"The topological phononic results rely on the assertion that the selected uppermost phonon bands in the 12-13 THz range are \"well separated bands,\" but no quantitative justification is provided. The manuscript does not give the minimum direct gap between this manifold and the lower phonon branches anywhere in the Brillouin zone, does not compare the Wannier-interpolated bands used for the surface and Berry-curvature calculations with the original DFPT phonon dispersion, and reports no band-entanglement or localization analysis. If the chosen manifold hybridizes with lower branches, the Wannier interpolation can produce incorrect Berry curvature, incorrect Chern numbers, and spurious surface arcs. This validation is essential because the phononic topology is half of the paper's central coexistence claim.","section":"Phononic Topology (Fig. 6)"},{"comment":"The paper assigns chirality -2 to the phononic Γ node and +2 to the phononic R node and shows surface Fermi arcs connecting them, but no direct calculation of the Chern number or Berry flux for the phonon manifold is presented. The authors should report the computed topological charges of the selected 12-13 THz manifold and demonstrate that these charges are stable under the Wannier interpolation. Without this, the assignment of the arcs' endpoints and the claim that the Γ and R nodes carry opposite chirality of ±2 are not established.","section":"Phononic Topology (Fig. 7)"}],"minor_comments":[{"comment":"The comparison of the optimized lattice parameter (a=4.78 Å) with experiment cites Ref. [42], which is titled \"The structure of HfSn.\" This reference does not appear to pertain to SiTc; please verify the correct experimental source for SiTc or correct the citation.","section":"Results and Discussion (lattice parameter)"},{"comment":"The phrase \"longest possible chiral open Fermi arc\" is an overclaim, since no comparison with other materials or a quantitative definition of \"longest\" is provided. Please replace it with a more modest descriptor such as \"long Fermi arc\" or provide the supporting comparison.","section":"Phononic Topology (Fig. 7)"},{"comment":"The text says the Fermi arcs originate \"from above and below Weyl points of the Γ point and not exectly from Γ point,\" which is consistent with the earlier statement that the Γ node carries no net chirality; however, the phrasing is confusing. Please reword to state explicitly that the arc endpoints are the nearby Weyl points, not the Γ point itself.","section":"Electronic surface states (Fig. 4)"},{"comment":"The manuscript contains numerous typographical and grammatical errors, including \"preformed,\" \"seprated,\" \"exectly,\" \"corrosponding,\" \"inculsion,\" \"degenarte,\" \"intrested,\" \"upermost,\" and \"hemiltonian.\" A thorough proofreading is needed.","section":"Throughout"},{"comment":"The sentence \"As the phononic system do not follow the pauli exclusion principle, allow to show the topological properties to entire frequency range\" is unclear and grammatically incorrect; please rewrite it to explain the intended point about phonons not being constrained by fermionic statistics.","section":"Phononic Topology"}],"recommendation":"major_revision","confidential_remarks":"The main blocker is the lack of validation for the phononic Wannier interpolation and the absence of a Chern-number calculation for the phonon manifold. The symmetry section's contradictory commutation relations are also a serious internal issue that must be fixed. The electronic part appears to be on firmer ground, but the manuscript needs careful proofreading and correction of the reference error before it can be considered for publication."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The paper is a DFT topology study of SiTc (space group 198) arguing that it hosts both topological electronic and phononic excitations. The electronic part is credible and mostly routine: the symmetry analysis for three-/four-fold nodes at Γ and R without SOC, evolving to four-/six-fold with SOC, follows the standard chiral-crystal framework, the Weyl chiralities sum to zero as required, and the surface states and spin Hall conductivities are computed with standard methods. That half of the paper reads like a solid, if incremental, characterization. The genuinely new content is the phononic side—three-/four-fold bosonic nodes at Γ/R and the chiral surface arcs—which was already demonstrated for RhGe (ref 26), so the framework is not new, but the specific prediction for SiTc is.\n\nThe soft spot is load-bearing. The phonon topology rests entirely on the choice of the uppermost 12–13 THz bands, which the authors call 'well separated' without giving a quantitative gap, any comparison between the DFPT dispersion and the Wannier-interpolated bands, or an entanglement analysis. Looking at Figure 6, the 12–13 THz manifold appears to touch lower branches near Γ in the full dispersion; the zoomed panels may be hiding that. If those bands hybridize anywhere in the BZ, the Wannier interpolation can produce incorrect Berry curvature, wrong Chern numbers, and spurious surface Fermi arcs. This should be a relatively easy fix—compute the gap to the next manifold, overlay the interpolated bands on the DFPT bands, and run a band-entanglement check—but without it the phononic half of the headline coexistence claim is not established.\n\nThere are two smaller issues. The 'longest possible Fermi arc' statement in the phononic section is an overclaim unless backed by a comparative survey. And ref [42] is cited for experimental synthesis of SiTc, but the reference is to HfSn; that citation looks wrong and weakens the claim that this material is already synthesized. The writing has many typos and awkward constructions, but that is cosmetic. I should also note that technetium has no stable isotopes, so any device-oriented discussion is speculative, though that does not affect the math.\n\nOverall: this is a plausible candidate paper, not a settled result. The electronic section alone could justify a modest publication; the phononic section needs the missing validation before the coexistence claim is taken seriously. I would send it to a competent referee with instructions to focus on the band-isolation issue, rather than desk-reject.","headline":"The phonon half of the coexistence claim needs a quantitative band-isolation check before I'd trust the surface arcs; the electronic side is standard, plausible, and internally consistent.","tokens_in":697,"tokens_out":916,"would_cite":false,"duration_ms":31700,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["71.20.-b","63.20.-e","72.25.-b","73.43.-f"],"model":"deepseek-v4-flash","headline":"SiTc is a chiral crystal in which symmetry-protected multifold nodes, Weyl points, Fermi arcs, and large spin Hall conductivity in the electrons are mirrored by topological nodes and surface arcs in the phonons.","keywords":["SiTc","chiral crystal","multifold fermions","topological phonons","Weyl points","Fermi arcs","spin Hall conductivity","space group 198"],"falsifier":"Compare the Wannier-interpolated phonon bands directly against the density-functional-perturbation-theory phonon dispersion across the full Brillouin zone; if the 12–13 THz branches overlap or entangle with lower branches, recompute the Chern numbers and surface arcs from the full phonon Hamiltonian and check whether the claimed topology survives.","tokens_in":11088,"feed_emoji":"⚛️","tokens_out":6915,"duration_ms":72902,"temperature":0.7,"pith_summary":"This paper argues that the already-synthesized chiral crystal SiTc is a rare material that is topologically nontrivial in both its electronic and its vibrational (phononic) spectra at the same time. Using density functional theory plus symmetry analysis, it identifies protected multifold band crossings at high-symmetry points Γ and R, Weyl points with balanced chirality, open Fermi arcs, and sizable spin Hall conductivity in the electrons, and matching three-fold and four-fold nodes with chiral surface arcs in the phonons. If the predictions hold, SiTc would be a single platform for studying coupled electronic and phononic topology and for spin-transport applications.","feed_headline":"SiTc crystal predicted to be topological for electrons and phonons","feed_subtitle":"Multifold nodes, Weyl points and Fermi arcs appear in both the electronic and vibrational bands of one crystal.","key_machinery":"The argument is carried by a symmetry analysis of the non-symmorphic screw rotations and three-fold rotations of space group 198: at Γ the screw operators commute and square to +1 in the spinless case, producing a three-dimensional irreducible representation, while at R they anticommute and square to −1, forcing a four-fold spinless degeneracy and, with spin-orbit coupling, a six-fold one. The same group-theoretic constraints are then applied to the phonon bands, whose degeneracies are governed by identical crystalline symmetries, and Wannier-interpolated tight-binding models are used to extract surface states, Fermi arcs, Berry curvature, and spin Berry curvature.","core_discovery":"The central claim is that in SiTc (chiral cubic space group 198), symmetry-enforced band degeneracies come in matched electronic and phononic versions. In the electron spectrum without spin-orbit coupling, the Γ point carries a three-fold (spin-1) node and the R point a four-fold (double spin-1/2) node; with spin-orbit coupling these become four-fold at Γ and six-fold at R, plus Weyl nodes labeled W1–W6 whose chiralities sum to zero across the Brillouin zone. The paper computes surface states with open Fermi arcs and Berry curvature consistent with those nodes, and a spin Hall conductivity whose dominant contributions come from near the multifold nodes. In the phonon spectrum it identifies a three-fold node at Γ and a four-fold charge-2 Dirac node at R in the 12–13 THz range, with surface Fermi arcs connecting nodes of chirality ±2. The conclusion is that SiTc simultaneously hosts topological fermionic and bosonic excitations.","pith_inferences":["Beyond the paper, the same symmetry relations should predict multifold topological phonons in other binary compounds with space group 198, so the set of candidate materials could be expanded by screening existing crystal databases.","The near-Fermi multifold nodes and large spin Berry curvature suggest that strain or doping could tune the chemical potential onto a four-fold or six-fold node to maximize the spin Hall response, an extension the paper only partially explores through shifted chemical potentials.","A natural experimental test would combine angle-resolved photoemission for the electronic Fermi arcs with inelastic X-ray scattering or time-domain phonon spectroscopy for the phononic arcs; clean surface preparation of SiTc would be the main technical obstacle."],"forward_implications":["SiTc should show open chiral Fermi arcs on (001) surfaces connecting the Weyl and multifold nodes, with mirrored arcs on the upper and lower surfaces.","The intrinsic spin Hall conductivity is sizable, reaching about 258–291 ℏ/e for the computed components at shifted chemical potentials, so SiTc could act as a spin-current source.","Phonons in the 12–13 THz window should exhibit chiral surface modes and long open Fermi arcs in the phononic spectrum, robust against backscattering.","Because the total chiral charge in the electronic Brillouin zone sums to zero, any chirality-driven transport signatures must originate from Fermi-arc surface states rather than net bulk chirality."],"supporting_citations":[{"why":"Supplies the theoretical classification of multifold fermions in chiral crystals that motivates the search in SiTc.","marker":"[11]"},{"why":"Provides the symmetry-protection relations for screw and three-fold rotations used to derive the allowed degeneracies at Γ and R.","marker":"[29]"},{"why":"Establishes the precedent of unconventional chiral fermions with the longest possible Fermi arcs in RhSi, the benchmark for the arc features claimed here.","marker":"[14]"},{"why":"Introduces double-Weyl phonons in transition-metal monosilicides, the conceptual basis for the four-fold charge-2 phonon node at R.","marker":"[28]"},{"why":"Supplies the maximally localized Wannier-function method used to construct the tight-binding model for surface-state calculations.","marker":"[36]"},{"why":"Provides the computational tool used to obtain surface states, Fermi arcs, and Berry curvature for both electrons and phonons.","marker":"[37]"},{"why":"Establishes the Kubo-type spin Berry curvature formalism used to compute the intrinsic spin Hall conductivity.","marker":"[40]"}],"fun_headline_variants":["SiTc hosts topological electrons and phonons together","Chiral crystal SiTc shows topological nodes in both bands","SiTc: one material, topological fermions and bosons","SiTc predicted to sync electronic and phononic topology"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The topological phonon claims rest on the assumption that the uppermost three phonon bands (12–13 THz) are genuinely separate from all lower vibrational bands, so the computed Chern numbers and surface arcs are not contaminated by mixing with other branches.","fun_headline_variants_meta":{"raw":{"variants":["SiTc hosts topological electrons and phonons together","Chiral crystal SiTc shows topological nodes in both bands","SiTc: one material, topological fermions and bosons","SiTc predicted to sync electronic and phononic topology"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000415,"raw_usage":{"total_tokens":2124,"prompt_tokens":910,"completion_tokens":1214,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":526,"completion_tokens_details":{"reasoning_tokens":1149}},"tokens_in":526,"tokens_out":1214,"duration_ms":9530,"temperature":1.0,"reasoning_tokens":1149,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-06T21:37:41.408873+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Compare the Wannier-interpolated phonon bands directly against the density-functional-perturbation-theory phonon dispersion across the full Brillouin zone; if the 12–13 THz branches overlap or entangle with lower branches, recompute the Chern numbers and surface arcs from the full phonon Hamiltonian and check whether the claimed topology survives.","supporting_citations":[{"cited_title":"Beyond dirac and weyl fermions: Unconventional quasiparticles in conventional crystals,","cited_arxiv_id":null,"evidence_quote":"Supplies the theoretical classification of multifold fermions in chiral crystals that motivates the search in SiTc."},{"cited_title":"Symmetry protection and giant fermi arcs from multifold fermions in binary, ternary, and quater- nary compounds,","cited_arxiv_id":null,"evidence_quote":"Provides the symmetry-protection relations for screw and three-fold rotations used to derive the allowed degeneracies at Γ and R."},{"cited_title":"Unconventional chiral fermions and large topological fermi arcs in rhsi,","cited_arxiv_id":null,"evidence_quote":"Establishes the precedent of unconventional chiral fermions with the longest possible Fermi arcs in RhSi, the benchmark for the arc features claimed here."},{"cited_title":"Double-weyl phonons in transition-metal monosilicides,","cited_arxiv_id":null,"evidence_quote":"Introduces double-Weyl phonons in transition-metal monosilicides, the conceptual basis for the four-fold charge-2 phonon node at R."},{"cited_title":"wannier90: A tool for obtain- ing maximally-localised wannier functions,","cited_arxiv_id":null,"evidence_quote":"Supplies the maximally localized Wannier-function method used to construct the tight-binding model for surface-state calculations."},{"cited_title":"Wanniertools: An open-source software package for novel topological materials,","cited_arxiv_id":null,"evidence_quote":"Provides the computational tool used to obtain surface states, Fermi arcs, and Berry curvature for both electrons and phonons."},{"cited_title":"Intrinsic spin hall effect in platinum: First-principles calculations,","cited_arxiv_id":null,"evidence_quote":"Establishes the Kubo-type spin Berry curvature formalism used to compute the intrinsic spin Hall conductivity."}],"review_version":1}