{"id":"2e6ff798-8613-4d01-b59d-b9a2e661bd04","arxiv_id":"2508.20338","paper_version":1,"verdict":"REJECT","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"high","formal_verification":"none","parameter_count":0,"one_line_summary":"Chiral lead-iodide perovskites show large circular-polarization-dependent Raman intensity differences that the authors attribute to chiral phonons, supported by DFT phonon angular momentum calculations.","lead":"The paper reports that circularly polarized laser light produces strongly different low-frequency Raman spectra in chiral lead-iodide perovskite crystals, an effect the authors call Raman optical activity. If confirmed, this would provide a new probe of chirality transfer and chiral phonons in hybrid perovskites.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The measured RCP/LCP Raman intensity difference is not established as ROA: the paper attributes it to preferential absorption, yet reports no 785-nm CD, and Table 1 frequency mismatches imply different modes rather than the same mode scattering differently.","rationale":"The reader's weakest_assumption identifies the same load-bearing concern: the paper conflates circularly polarized excitation-dependent intensity differences with Raman optical activity while itself attributing those differences to preferential absorption of RCP or LCP light. This is not a peripheral issue; the abstract's central claim depends on the RCP/LCP intensity asymmetry being an intrinsic chiroptical property of the phonon modes. The DFT phonon angular momentum calculations are plausible and extend prior computational work on (S-MBA)2PbI4, so the existence of chiral phonons in the calculated structure is not the main weakness. The weakness is the experimental connection: the measured asymmetry has not been separated from circular dichroism of the incident beam, and the Table 1 frequency differences between RL and LR spectra suggest that different vibrational modes are selected in different polarization configurations, which would invalidate the mode-resolved ROA interpretation. The absence of a 785-nm CD measurement is particularly telling because the paper claims sub-bandgap, non-resonant excitation while also invoking preferential absorption as the source of the intensity differences. These are load-bearing flaws in the central claim, not minor omissions. The reader's REJECT verdict is appropriate, and my analysis does not change that verdict.","tokens_in":11888,"tokens_out":4415,"duration_ms":45024,"concrete_test":"Measure polarization-resolved circular dichroism (RCP vs LCP transmission) of the same (R/S-NEA)PbI3 single crystals at 785 nm using the identical beam path, focusing geometry, and polarization states used in the Raman experiment. If the 785-nm CD is negligible (<1%) and the RL/LR Raman asymmetry persists after normalizing to transmitted power, the effect is likely intrinsic Raman scattering; if the 785-nm CD is comparable to the observed Raman asymmetry, the reported ROA is dominated by preferential absorption and does not establish chiral phonon ROA.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central experimental observable is the difference between RL and LR (or RR and LL) Raman spectra, which the paper labels ROA. This label is load-bearing because the abstract and conclusions assert that chiral phonons produce strong Raman optical activity. However, the paper itself states in the Results and Discussion (Figure 2 discussion) that the large intensity variations 'are due to preferential absorption of RCP or LCP excitation by the two CHOIP enantiomers.' Preferential absorption of the excitation beam is circular dichroism in the optical path, not a property of the Raman scattering tensor, and it does not by itself demonstrate ROA of the phonon modes. The 785 nm excitation is claimed to be sub-bandgap and non-resonant, yet no CD or polarization-resolved transmission measurement at 785 nm is reported, so the magnitude of absorption-induced asymmetry is unknown. The problem is compounded by Table 1: for the same nominal modes, the RL and LR frequencies differ substantially (e.g., 34.1 vs 31.1, 47.6 vs 42.8, 52.7 vs 46.6, 94 vs 101.1 cm-1). If the same phonon is being excited, its frequency should be independent of the circular polarization combination; the observed shifts indicate that different modes are being selected, so computing IRL - ILR at fixed wavenumbers does not measure the ROA of a single mode. Without separating absorption CD from scattering ROA and verifying mode identity across polarization configurations, the central claim of strong phonon ROA is unsupported.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports the synthesis and characterization of chiral hybrid organic-inorganic perovskites (CHOIPs) based on R/S-NEA, R/S-PEA, D/L-alanine, and D/L-proline cations, and presents low-frequency circularly polarized Raman spectra (785 nm excitation) alongside DFT calculations of phonon modes and phonon angular momentum (PAM). The authors claim strong Raman optical activity (ROA) with circular intensity differences as high as 0.73, attribute the effect to chirality transfer from the organic linkers to the PbI3 octahedra, and identify several chiral phonon modes with opposite PAM from first-principles calculations. The central claim is that circularly polarized light selectively excites low-frequency Raman-active modes of the lead-iodide sublattice and that these modes carry phonon angular momentum.","tokens_in":12061,"tokens_out":7015,"duration_ms":60377,"significance":"If fully substantiated, this work would be a notable advance in chiroptical spectroscopy of hybrid perovskites, offering a new probe of chirality transfer and chiral phonons in solids. The DFT calculations and PAM analysis follow standard, transparent methods, and the paper provides crystallographic data (CCDC), detailed synthetic procedures, and temperature-dependent measurements, which are commendable. However, the experimental ROA claim is undermined by the paper's own attribution of the observed intensity differences to preferential absorption of the excitation beam rather than to a chiral Raman scattering tensor, and by the absence of a 785-nm circular dichroism baseline. The mode-level interpretation is further weakened by substantial mismatches between RL and LR peak frequencies in Table 1. The computational identification of chiral phonons is independent and valuable, but it does not rescue the central experimental conclusion.","major_comments":[{"comment":"The paper states that the large variation in peak intensities between RL and LR spectra is 'due to preferential absorption of RCP or LCP excitation by the two CHOIP enantiomers,' yet it subsequently defines the difference as Raman optical activity. Preferential absorption is circular dichroism of the excitation beam, not a property of the Raman scattering tensor, so the difference does not by itself measure ROA of the phonon modes. No CD or polarization-resolved transmission measurement at 785 nm is reported, despite the excitation being sub-bandgap, so the magnitude of absorption-induced asymmetry is unknown. This conflation is load-bearing and invalidates the central claim of strong ROA.","section":"Results and Discussion (Figure 2 discussion)"},{"comment":"The peak frequencies listed for the RL and LR configurations differ substantially for the same nominal modes: peak 4 at 34.1 versus 31.1 cm-1, peak 6 at 47.6 versus 42.8 cm-1, peak 7 at 52.7 versus 46.6 cm-1, and peak 9 at 94 versus 101.1 cm-1. If the same phonon is being excited in both configurations, its frequency should be independent of the circular polarization combination; the observed differences indicate that different modes are selected in RL versus LR. Consequently, computing IRL - ILR at fixed wavenumbers does not measure the ROA of a single mode, and the mode-level interpretation of the ROA and CID spectra is not justified.","section":"Table 1"},{"comment":"The statement that calculated peaks are blue-shifted by 'between 0.7 - 7.7 cm-1' is contradicted by Table 1: peak 9 (measured 75.4 versus calculated 83.7 cm-1) differs by 8.3 cm-1, peak 10 (90.8 versus 99.8 cm-1) by 9.0 cm-1, and peak 11 (107.5 versus 105.8 cm-1) is red-shifted. The larger deviations indicate that the assignment of several experimental peaks to specific calculated modes is insecure, which further weakens the claimed correspondence between calculated chiral phonons and experimental ROA features.","section":"Results and Discussion (text preceding Table 1)"},{"comment":"The circular intensity difference is defined as (IR - IL)/(IR + IL), with the text stating that 'IR + IL represents unpolarized spectra.' However, the unpolarized spectra were measured separately, not as the sum of RL and LR intensities, so the denominator is not the total scattered intensity for the same scattering configuration. The quantitative CID values, including the peak value of 0.73, are therefore not a well-defined standard circular intensity difference and may be dominated by differences in excitation throughput between polarization configurations unless a common normalization is established.","section":"Results and Discussion (ROA definition and CID)"}],"minor_comments":[{"comment":"Typo: 'we well as structural metrics' should read 'as well as structural metrics.'","section":"Introduction"},{"comment":"The caption writes '(R/S-NEA)PBI3'; the chemical formula should be PbI3, not PBI3.","section":"Figure 2 caption"},{"comment":"'mucasol/ DI water' should be 'Mucasol/DI water' for clarity.","section":"Experimental section"},{"comment":"The symbol 'G point' is used in place of the standard notation 'Γ point'; this should be corrected for consistency with the literature.","section":"Throughout"},{"comment":"The phonon angular momentum expression in the text contains a garbled symbol ('%') in the matrix product; please typeset the equation correctly.","section":"Computational Details"},{"comment":"The calculated frequency column is not labeled with units; add 'cm-1' for consistency with the measured columns.","section":"Table 1"},{"comment":"The conclusions state that the experimental modes 'exhibit opposite phonon angular momenta due to their chiral nature,' but the text near Figure 6 acknowledges that the splitting is too small to measure and that the correspondence between calculated and measured modes is difficult to establish; the conclusions should be moderated accordingly.","section":"Conclusions"}],"recommendation":"reject","confidential_remarks":"The paper's central experimental claim of strong Raman optical activity is internally contradicted by the authors' own statement that the intensity differences arise from preferential absorption of the excitation beam. The missing 785-nm CD control and the large RL/LR frequency mismatches in Table 1 compound the problem, making the ROA and CID analyses unreliable. The DFT calculations of chiral phonons are a useful contribution, but they are presented as confirmation of the experimental ROA, which is not established. I would not rule out a future study that properly separates absorption effects from scattering effects, but the current manuscript does not support its headline claims."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"What you need to know: this paper has a genuinely new experimental dataset and a plausible DFT calculation of phonon angular momentum, but its central interpretation—that the measured circular intensity differences are Raman optical activity—is not supported. The authors themselves say the differences come from preferential absorption of RCP/LCP excitation, which is circular dichroism in the optical path, not phonon ROA. They never measure CD at 785 nm to quantify that absorption asymmetry, and Table 1 shows the 'same' modes appearing at different frequencies in RL vs LR (e.g., 52.7 vs 46.6 cm-1), which suggests different modes are being selected rather than one mode scattering differently. That combination undercuts the headline claim.\n\nWhat's good: the synthesis and characterization across four chiral perovskite families is careful; the low-frequency modes with narrow linewidths are interesting; the DFT calculation reproduces the 12 unpolarized Raman peaks reasonably well, and the phonon angular momentum calculation for (S-NEA)PbI3 (P212121, chiral phonons near 10.7 and 58.5 cm-1) is a legitimate, standard computation that extends prior work on (S-MBA)2PbI4. If the paper were just about chiral phonons in these materials and the polarization-dependent Raman as a qualitative observation, it would be a solid contribution.\n\nSoft spots beyond the ROA conflation: the stated blueshift range (0.7–7.7 cm-1) is contradicted by Table 1, which has differences up to 9.0 cm-1 and some redshifts. The mode assignment in Figure 5 (dots at the Gamma point) is loose—they admit the splitting is too small to measure, so the experimental connection to chiral phonons is indirect. The CID of 0.73 is so far above typical ROA values that it should have been a red flag that you're not measuring the same thing.\n\nWho is this for? Researchers in chiral phononics and chiroptical spectroscopy. It's worth a serious referee, but not as is—the authors need to either measure the 785-nm CD and subtract it, or reframe the paper as circularly polarized Raman modulated by absorption, not ROA. I'd encourage you to send it out for review, but the verdict should be major revision at best.","headline":"First circularly polarized Raman study on chiral perovskites, but the central ROA claim is undone by the paper's own absorption explanation and missing CD baseline; the DFT phonon angular momentum work stands on its own.","tokens_in":12739,"tokens_out":3799,"would_cite":false,"duration_ms":33489,"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":"Circularly polarized excitation produces large, enantiomer-dependent intensity differences in the low-frequency Raman spectra of chiral hybrid perovskites, and calculations identify the active modes as chiral phonons with opposite angular…","keywords":["chiral perovskites","hybrid organic-inorganic perovskites","circular polarization","Raman optical activity","chiral phonons","phonon angular momentum","lead iodide octahedra","chiroptical spectroscopy"],"falsifier":"Measure the same enantiomer's Raman spectra with a fixed incident circular polarization while switching only the detected circular polarization, and also record how I_R - I_L scales with crystal thickness and excitation wavelength; if the asymmetry scales with absorbed power and follows the circular dichroism spectrum, it is absorption-gated rather than phonon ROA, whereas if it survives normalization by absorbed power and changes with detection handedness, the chiral scattering tensor claim is supported.","tokens_in":11592,"feed_emoji":"🔬","tokens_out":9210,"duration_ms":86648,"temperature":0.7,"pith_summary":"This paper reports that the low-frequency Raman modes of the lead-iodide sublattice in chiral hybrid organic-inorganic perovskites respond strongly to the handedness of circularly polarized excitation. In single crystals of several chiral ammonium- and amino-acid-based perovskites, modes below 150 cm-1 appear, disappear, or change intensity between right- and left-circular excitation, with circular intensity differences as high as 0.73, orders of magnitude above typical molecular Raman optical activity. First-principles phonon calculations identify modes with finite phonon angular momentum of opposite sign, i.e. chiral phonons. The authors argue that both effects follow from chirality transfer from the chiral organic cation to the lead-iodide octahedra, making circularly polarized Raman a direct probe of structural chirality in these materials.","feed_headline":"Chiral perovskites show strong Raman optical activity in their phonons","feed_subtitle":"Low-frequency octahedral modes show circular-intensity differences up to 0.73, pointing toward phonon-selective chiral optics.","key_machinery":"The experimental machinery is the circularly polarized Raman measurement in co- and cross-circular configurations (RR, LL, RL, LR), with Raman optical activity defined as the intensity difference I_R - I_L and quantified by the circular intensity difference (I_R - I_L)/(I_R + I_L). The theoretical machinery is the phonon angular momentum expression J = ℏ u^† M^α u, where M^α is built from the Levi-Civita tensor and projects phonon eigenvectors onto rotational motion. The chain that carries the argument is: circular dichroism near the band edge proves chirality transfer; low-frequency Raman peaks are assigned to Pb-I octahedral vibrations; the strongly asymmetric modes coincide with calculated modes carrying finite phonon angular momentum; and the near-perfect enantiomer swap in the spectra links the intensity asymmetry directly to the handedness of the crystal.","core_discovery":"The central claim is that chirality transfer from the chiral organic cation to the lead-iodide octahedra makes the low-frequency phonons of chiral hybrid organic-inorganic perovskites intrinsically chiral, so that right- and left-circularly polarized excitation produces markedly different Raman spectra. For each enantiomer pair, the RL spectrum of one crystal matches the LR spectrum of the other, meaning the polarization asymmetry swaps with molecular handedness. First-principles phonon calculations reproduce all twelve observed peaks and assign the strongly asymmetric modes to Pb-I octahedral vibrations; phonon angular momentum calculations yield modes with opposite signs of Jx, Jy, and Jz along different Brillouin-zone directions, including a pair near 10.7 cm-1 whose atoms rotate clockwise and anticlockwise with near-unity angular momentum. The paper concludes that the strong Raman optical activity and the chiral phonon modes are direct consequences of the chiral distortion of the octahedral sublattice, making circularly polarized Raman a broadly applicable probe of chirality transfer in CHOIPs.","pith_inferences":["The paper does not separate absorption-gated selection from scattering-tensor ROA in its static optical setup; a thickness- and wavelength-dependent study would test whether the reported I_R - I_L asymmetry scales with circular dichroism absorption.","The perfect enantiomer swap (RL of the R crystal equals LR of the S crystal) hints that preferential absorption of one circular polarization before an otherwise identical Raman scattering event may dominate; if so, the effect is better called circular-dichroism-gated Raman rather than conventional phonon ROA, while the calculated chiral phonons would still stand.","Extending the measurements toward the band edge or to resonant excitation could reveal whether chiral phonons couple to excitons in the lead-iodide sublattice, linking phonon angular momentum to the circularly polarized luminescence already known in these materials.","The same phonon angular momentum analysis should transfer to other chiral space groups, offering a screening criterion: materials with large computed phonon angular momentum in low-frequency modes are the best candidates for observing mode-selective circular polarization effects."],"forward_implications":["Low-frequency circularly polarized Raman becomes a general, sub-bandgap diagnostic for chirality transfer in chiral hybrid organic-inorganic perovskites, applicable across a wide range of chiral organic cations.","If the phonons genuinely carry angular momentum, resonant or near-resonant excitation could couple chiral phonons to electronic spin or valley degrees of freedom, enabling control of circularly polarized luminescence in these materials.","The high degree of circular polarization, with CID up to 0.73, implies that individual octahedral modes can be selectively pumped by choosing the handedness of the excitation, a step toward chiral Raman lasers and circular polarization filters.","The persistence of narrow Raman lines from 100 to 400 K indicates that the chiral octahedral network is rigid against phase transitions, extending the useful operating range of CHOIP optoelectronic and phononic devices."],"supporting_citations":[{"why":"Computational prediction of low-frequency chiral phonons in the related 2D perovskite (S-MBA)2PbI4; supplies the expectation and comparison target for the phonon angular momentum calculation.","marker":"[35]"},{"why":"Defines the phonon angular momentum operator J = ℏ u^† M^α u used to compute the chiral phonon angular momenta.","marker":"[39]"},{"why":"Extends the phonon angular momentum formalism and is cited together with [39,41] for the PAM expression.","marker":"[40]"},{"why":"Provides the angular momentum projection used to identify chiral phonons in the DFT phonon eigenvectors.","marker":"[41]"},{"why":"Classic theory of Raman optical activity and circular intensity difference; sets the reference point for typical CID magnitudes that the measured values far exceed.","marker":"[37]"},{"why":"Recent circularly polarized Raman measurements on two-dimensional materials with high CIDs; the comparison baseline for the unusually large circular intensity differences reported here.","marker":"[34]"},{"why":"Report of broadened low-frequency Raman modes in achiral hybrid perovskites due to anharmonic polar fluctuations; the sharp peaks measured here are contrasted with this result.","marker":"[19]"},{"why":"Crystal structure reference for (S-NEA)PbI3 that supplies the initial experimental structures for the DFT relaxations.","marker":"[46]"}],"fun_headline_variants":["Chiral perovskites reveal strong Raman optical activity in phonons","Chiral phonons in perovskites flip circularly polarized Raman","Raman probes handedness of phonons in chiral perovskites","Octahedral phonons show chiral response in perovskites","Chirality transfer lights up phonon Raman in perovskites"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The paper's load-bearing premise is that the difference between right- and left-circularly excited Raman spectra is Raman optical activity of the phonon modes, even though the paper itself says the difference is due to preferential absorption of the two circular polarizations by the enantiomers; if absorption rather than a chiral scattering tensor drives the asymmetry, the central claim of strong phonon ROA would need to be reformulated.","fun_headline_variants_meta":{"raw":{"variants":["Chiral perovskites reveal strong Raman optical activity in phonons","Chiral phonons in perovskites flip circularly polarized Raman","Raman probes handedness of phonons in chiral perovskites","Octahedral phonons show chiral response in perovskites","Chirality transfer lights up phonon Raman in perovskites"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000599,"raw_usage":{"total_tokens":2830,"prompt_tokens":1006,"completion_tokens":1824,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":622,"completion_tokens_details":{"reasoning_tokens":1739}},"tokens_in":622,"tokens_out":1824,"duration_ms":12355,"temperature":1.0,"reasoning_tokens":1739,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-15T16:46:36.156902+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the same enantiomer's Raman spectra with a fixed incident circular polarization while switching only the detected circular polarization, and also record how I_R - I_L scales with crystal thickness and excitation wavelength; if the asymmetry scales with absorbed power and follows the circular dichroism spectrum, it is absorption-gated rather than phonon ROA, whereas if it survives normalization by absorbed power and changes with detection handedness, the chiral scattering tensor claim is supported.","supporting_citations":[],"review_version":1}