{"id":"267a30bc-98ee-434b-a5b4-6189a1790dea","arxiv_id":"1908.06787","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"Thin neon films on porous glass stiffen below about 7 K with a dissipation peak near 5 K, showing a classical counterpart to helium's elastic anomaly with no quantum phase transition.","lead":"Neon films squeezed into nanoscale pores of porous glass get measurably stiffer when cooled below about 7 kelvin, with a sharp rise in mechanical loss. The pattern resembles a similar anomaly in helium films, but the transition temperature stays near 5 kelvin instead of dropping to zero, which the authors read as a sign that neon is a classical, not quantum, film.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The 5 K dissipation peak that fixes Tp is assumed to be intrinsic, yet the same torsional oscillator shows unexplained resonant anticrossing peaks (Sect. 3.2, Fig. 3 inset); if the broad peak is a mechanical coupling artifact, the coverage-independent Tp and the no-QPT conclusion do not follow.","rationale":"The paper is a credible experimental report: raw f and Q^{-1} data visibly show a neon-induced stiffening crossover with a dissipation peak, the n=0 background is measured, the density-loading correction (Eq. 3) is negligible, and the low-temperature frequency shift grows linearly with coverage with an offset. These observations stand independently of the model. The weakest link is not the data but the interpretation of the 5 K peak as an intrinsic film response. The authors themselves report unexplained resonant anticrossing peaks in the same apparatus, so the mechanical-coupling hypothesis is not ad hoc; it is a documented failure mode. The fit parameters that would make the anelastic model quantitative are unphysical and are flagged as such in the manuscript, so the model cannot independently validate the identification of Tp. A frequency-variation experiment would settle the question cleanly because an intrinsic Debye peak has a characteristic weak logarithmic frequency dependence, while a coupled mechanical mode should be strongly sensitive to oscillator parameters. Because the concern is unresolved rather than demonstrated, the appropriate outcome remains the reader's conditional acceptance: the main claims are plausible but require this check before the no-QPT and universality statements are treated as established.","tokens_in":10621,"tokens_out":7719,"duration_ms":89654,"concrete_test":"Change the torsional oscillator's frequency by at least a factor of 3 (e.g., install a bob with different moment of inertia or a stiffer torsion rod) and remeasure a film at n=20 µmol/m². For the intrinsic anelastic model, Eq. (7) predicts Tp = E/[kB ln(1/(ωτ0))]; using the authors' fit-Q values (E/kB≈122 K, τ0≈4×10⁻¹⁵ s), increasing f from 859 Hz to 2.6 kHz shifts Tp by only ~0.2 K, and the low-temperature stiffening step in 2δf/f0 should persist. If the 5 K peak instead disappears, shifts by more than 1 K, or develops a sharp anticrossing in f(T), the peak is a resonant coupling artifact and the no-QPT claim is unsupported. A complementary check at two drive amplitudes (e.g., factor of 5) would distinguish linear anelastic relaxation from a nonlinear coupled mode.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim—that neon films behave classically because Tp saturates near 5 K rather than extrapolating to 0 K—rests on identifying the 5 K dissipation peak as an intrinsic anelastic response of the neon film. The manuscript itself documents a failure mode of this assumption: sharp dissipation peaks with resonant-frequency anticrossing appeared in runs at 13–35 µmol/m² (Sect. 3.2, inset of Fig. 3(a)). The authors state that the anticrossing 'clearly originates from a resonant coupling of some vibration mode (e.g., sound wave) in the neon film or porous glass to torsional oscillation' and that it remains unexplained. If the broad 5 K peak arises from a similarly coupled film/substrate mode rather than from thermally activated relaxation of adsorbed neon, then Tp is not a property of the film's intrinsic dynamics; the constancy of Tp above 10 µmol/m² would be a property of the mechanical mode, and the inferred absence of a quantum phase transition would lose its main support. The unphysical thermal-activation fit (fit-Q gives τ0≈4 fs and τ0Δ below ℏ, Sect. 3.3), also self-flagged by the authors, weakens the quantitative model but does not by itself disprove the raw Tp observation; the resonance question is the more load-bearing concern. The broadness and monotonic stiffening of the main anomaly make a simple sharp anticrossing unlikely at 5 K, so the concern does not force rejection, but it is precisely the condition that needs independent confirmation.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports torsional oscillator measurements of thin neon films adsorbed on porous glass (Gelsil) from 1.2 K to about 25 K. For coverages above 10 µmol/m², the resonant frequency increases below about 10 K and an accompanying dissipation peak appears at T_p ≈ 5 K. The authors interpret this as an anelastic crossover from a high-temperature fluidlike soft state to a low-temperature solidlike stiff state. They compare this behavior with their earlier helium film data, where T_p approaches zero at a critical coverage, and conclude that neon films behave classically, exhibiting neither a quantum phase transition nor superfluidity. They further propose that the elastic anomaly is probably a universal phenomenon of atomic or molecular films adsorbed on disordered substrates.","tokens_in":10996,"tokens_out":4605,"duration_ms":45603,"significance":"The raw frequency and dissipation data provide direct evidence of a reproducible stiffening crossover with a dissipation peak, and the authors are commendably transparent about problematic aspects of their analysis, including the unphysical thermal-activation fit parameters and the unexplained sharp anticrossing features. If the 5 K dissipation peak is an intrinsic anelastic response of the neon film, the result is significant because it demonstrates that the elastic anomaly occurs in a non-superfluid, weakly quantum adsorbate, thereby decoupling the anomaly from superfluidity and quantum phase transitions. The universality claim is directly falsifiable by experiments with other adsorbates or different disordered substrates, which adds to the paper's value.","major_comments":[{"comment":"The manuscript documents sharp dissipation peaks accompanied by resonant-frequency anticrossing in the 13–35 µmol/m² coverage range and states that this resonant coupling of a vibration mode in the neon film or porous glass to the torsional oscillator remains unexplained. The central conclusion that T_p saturates at about 5 K and therefore that neon films do not show a quantum phase transition assumes that the broad 5 K dissipation peak is an intrinsic anelastic response of the neon film. The authors should rule out a mechanical-coupling origin for this peak by providing concrete evidence, such as a demonstration that no frequency anomaly or anticrossing appears at T_p, a check of whether T_p is independent of the torsional oscillator's resonance frequency, or a showing that the peak amplitude evolves with coverage in a manner unlike a fixed vibrational mode.","section":"Section 3.2, inset of Fig. 3(a)"},{"comment":"The fit-Q analysis yields tau_0 = 4 fs and Delta/k_B = 122 K, and the authors correctly note that the product tau_0*Delta is smaller than Planck's constant, violating the time-energy uncertainty relation. This is a load-bearing quantitative failure of the proposed thermal activation model for neon. Because the model is used to infer an energy distribution and to draw comparisons with helium films, the manuscript should either identify a physical mechanism that could produce such a small apparent attempt time or explicitly state that the model is inadequate for neon and withdraw the quantitative fit parameters as evidence for a gapped energy spectrum.","section":"Section 3.3, fit-Q parameters"},{"comment":"The fitting to the dissipation data is performed after subtracting an 'extra background proportional to log(T)' from delta_Q^-1, but no independent measurement or physical justification for this background is provided. Because this subtraction is a fitted degree of freedom, the visual agreement of fit-Q with the dissipation data is partly built into the analysis. The authors should show the unsubtracted data and the form of the extra background, and discuss how the fitted parameters and the extracted T_p are affected by including or omitting this background.","section":"Section 3.3, Fig. 6"}],"minor_comments":[{"comment":"The caption writes '2δ(Tmin)/f0' but should be '2δf(Tmin)/f0' for consistency with the text.","section":"Fig. 4 caption"},{"comment":"The first two intended coverages (5 and 8 µmol/m²) were not properly prepared, and the reported n = 4.5 ± 1.0 µmol/m² has a large uncertainty. The single T_p ≈ 11 K point at this coverage should be presented with this caveat more prominently, as it anchors the steeply coverage-dependent part of the phase diagram.","section":"Section 2.2"},{"comment":"The claim that the disorder in δQ−1 at 20 K 'synchronizes with the pressure rise due to the melting of solid neon outside the PG' is not supported by any displayed pressure data; either show the pressure trace or remove this assertion.","section":"Section 3.2, paragraph beginning 'The disorder in δQ−1 at 20 K'"},{"comment":"The log-normal distribution F(E) is defined inline in the text; it would be clearer to display the function explicitly as an equation, since it is central to the fitting procedure.","section":"Eq. (8) and surrounding text"},{"comment":"Reference [11] cites unpublished results on hydrogen films; please label it as 'in preparation' or provide a preprint identifier so that the universality statement in the Conclusions is verifiable.","section":"Reference [11]"},{"comment":"The statement that 'there are only two phases in neon films adsorbed on PG' is inferred solely from the elastic anomaly; consider softening this to 'the elastic response indicates only two states' to avoid overinterpreting a single probe.","section":"Section 3.4, final paragraph"}],"recommendation":"major_revision","confidential_remarks":"The paper is within the scope of J. Phys. Soc. Jpn. and builds appropriately on the authors' previous helium film work. The main concern is whether the 5 K dissipation peak is intrinsic to the film dynamics or a mechanical coupling artifact, given that the same apparatus and measurement protocol produced the documented anticrossing features. If the authors can convince the reader on this point with existing or new data, the paper would be worthy of publication. The unphysical fit parameters are a weakness but are already self-flagged; however, they should be contextualized more carefully so they are not read as supporting evidence."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"First systematic elasticity measurements of neon films on porous glass, and the core observation is visible in the raw data: below about 10 K the torsional frequency stiffens by a coverage-dependent amount and a dissipation peak sits near 5 K. That is new. The comparison with helium films is the right frame, and the coverage-independent Tp for neon, in contrast to helium's Tp trending to zero, is a real result if the peak assignment holds. The paper also deserves credit for flagging that its own thermal-activation fit gives tau0 = 4 fs and tau0*Delta below h, i.e. unphysical parameters. Most authors would have hidden that.\n\nWhere are the soft spots? The fit-Q model is not load-bearing for the main claim; the anomaly is read directly off the data, and the fit is an attempt to quantify it. Still, the fit being unphysical matters because the authors use it to claim the anomaly has the same mechanism as helium. That inference is weaker than they present. More importantly, the claim about the classical/quantum distinction rests on the shape of Tp(n) below 10 µmol/m2, and there is only one usable coverage there, n = 4.5 ± 1.0 µmol/m2, with Tp around 11 K. One uncertain point is a thin reed for the statement that Tp \"strongly depends on coverage\" below 10 µmol/m2. The stress-test worry about resonant coupling from the sharp anticrossing peaks in Sect. 3.2 is, on reading the paper, less serious than it sounds. Those peaks are sharp, appear at 16–25 K, and show an anticrossing in the frequency; the 5 K anomaly is broad, reproducible, and has a monotonic f shift. A coupled mode would not naturally give a broad Debye-like peak. So I do not think the central observation is undermined, but the paper should explicitly address why the 5 K peak is not the same phenomenon.\n\nOther minor issues: negative deltaQ^-1 below 3 K is dismissed as also seen in helium, which is a bit hand-wavy; the log(T) \"extra background\" subtracted before fitting is another free parameter; and the phase diagram in Fig. 5 has very few low-coverage points. The paper would be strengthened by releasing raw data and by separating the model-dependent parameter discussion from the direct observation. The self-citation to the earlier helium work is legitimate since that is the same technique and the comparison is the point.\n\nThis paper is for people working on adsorbed films, 2D quantum solids, and low-temperature torsional oscillator measurements. It deserves a serious referee. I would send it out, probably asking for revision rather than accepting as-is.","headline":"First systematic look at neon film elasticity on porous glass; the raw stiffening crossover is real, the model fit is not, and the paper is worth refereeing with revision.","tokens_in":11500,"tokens_out":2713,"would_cite":true,"duration_ms":29314,"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":"Thin neon films on porous glass stiffen at low temperatures, with the dissipation peak pinned near 5 K independent of coverage, indicating a classical crossover without a quantum phase transition.","keywords":["neon films","elastic anomaly","torsional oscillator","porous glass","anelastic relaxation","quantum phase transition","thermal activation model","adsorbed films"],"falsifier":"A decisive test is to vary the torsional oscillator's resonant frequency by about a factor of two at fixed neon coverage and see whether the dissipation peak stays at 5 K: if it moves with frequency, the peak is a resonance artifact; if it stays, the thermal-activation interpretation is supported.","tokens_in":10415,"feed_emoji":"❄️","tokens_out":4963,"duration_ms":47700,"temperature":0.7,"pith_summary":"This paper reports that thin neon films adsorbed on porous glass become abruptly stiffer as the temperature drops, with excess mechanical dissipation peaking near 5 K. The authors interpret this as a crossover from a soft, fluidlike state to a stiff, solidlike state, mirroring an elastic anomaly previously seen in helium films. Unlike helium, however, the crossover temperature does not fall toward zero as film coverage is varied. The authors conclude that neon behaves classically, with no quantum phase transition or superfluidity, and that the elastic anomaly is a generic feature of atomic or molecular films on disordered substrates.","feed_headline":"Neon films on glass stiffen at 5 K; no quantum transition","feed_subtitle":"Unlike helium, the shear-modulus crossover stays near 5 K, showing neon film dynamics are classical.","key_machinery":"The central object is the torsional oscillator, which measures the change in resonant frequency and dissipation as neon is adsorbed; a finite-element analysis shows the frequency shift is dominated by the film's shear modulus rather than its mass. The argument's explanatory engine is the anelastic relaxation model: neon atoms occupy localized ground states separated by a distribution of energy gaps from extended states, with a thermally activated relaxation time $\\tau = \\tau_0 e^{E/k_B T}$. The model predicts the observed steplike increase in $2\\delta f/f_0$ and the accompanying dissipation peak when $\\omega\\tau \\approx 1$. A log-normal gap distribution and a single fitted attempt time $\\tau_0$ are used to match the data.","core_discovery":"Using a torsional oscillator, the authors measured the shear modulus of neon films (coverages roughly 4 to 40 µmol/m²) on porous glass down to 1.2 K. The resonant frequency shift shows the film's elasticity increasing by up to an effective shear modulus of about 40 MPa at low temperature, while dissipation peaks at about 5 K. They fit the response with a thermal activation model in which localized atoms are thermally excited into extended states with a distribution of energy gaps; the fit reproduces both the stiffening and the dissipation, though it requires an unphysically small attempt time. The central claim is that the dissipation peak temperature saturates at roughly 5 K independent of coverage, in contrast to helium where the peak temperature vanishes at a critical coverage marking a quantum phase transition. From this the authors conclude that neon films are classical and that the elastic anomaly is universal.","pith_inferences":["If the 5 K peak reflects the film's intrinsic glassy dynamics rather than a mechanical resonance, the coverage independence implies that the relevant energy barrier is set by the neon–porous-glass interaction, not by film thickness; this could be tested by varying pore size or using a different disordered substrate.","The unphysically small attempt time found in the fit may indicate that the two-state thermal activation picture is incomplete; a distribution of relaxation times or a non-Arrhenius law might describe the crossover better and could be tested by measuring how the peak shifts with oscillator frequency.","The apparent universality on disordered substrates suggests that torsional-oscillator stiffening could serve as a general probe of supercooled liquid dynamics in nanoconfinement, beyond the specific case of neon."],"forward_implications":["If the anomaly is universal, helium's elastic anomaly is not a fingerprint of superfluidity or a quantum phase transition, and similar stiffening should appear in other adsorbed films such as hydrogen, which the authors state they have observed.","Above roughly one monolayer, the dissipation peak's height saturates while the low-temperature elasticity still grows, implying that only the layer in contact with the substrate contributes to dissipation.","The crossover to the soft state resembles a dynamic glass transition, so cooling-rate or frequency-dependent measurements could test whether neon films exhibit glassy dynamics.","The phase diagram of neon on porous glass has only two effective states, stiff and soft, contrasting with the multiple phases seen on graphite."],"supporting_citations":[{"why":"Supplies the helium-film elastic anomaly and the thermal activation model that the neon data are compared with and fitted to.","marker":"[7]"},{"why":"Origin of the localized-atom thermal activation picture used for helium and now neon.","marker":"[18]"},{"why":"Extends the model and provides the comparison critical coverage for helium on porous glass.","marker":"[19]"},{"why":"Gives the anelastic relaxation response functions used in the fitting.","marker":"[20]"},{"why":"Provides heat-capacity evidence of two-dimensional phases of neon on graphite, the contrast for the disordered substrate.","marker":"[12]"},{"why":"Provides layer-by-layer growth and phase information on graphite, supporting the amorphous interpretation on porous glass.","marker":"[13]"},{"why":"Supplies the bulk solid neon shear modulus used to compare the film's effective stiffness.","marker":"[24]"}],"fun_headline_variants":["Neon films stiffen at 5 K: a universal elastic anomaly","Neon film's elastic anomaly stays put at 5 K","No quantum transition in neon films, only stiffening at 5 K","Neon films: classical stiffening, unlike helium's quantum switch","Elastic anomaly in neon films mirrors helium but stays classical"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The broad dissipation peak at about 5 K used to define the crossover is an intrinsic anelastic response of the neon film, not a spurious resonance arising from mechanical coupling between the oscillator and a film or porous-glass vibration mode.","fun_headline_variants_meta":{"raw":{"variants":["Neon films stiffen at 5 K: a universal elastic anomaly","Neon film's elastic anomaly stays put at 5 K","No quantum transition in neon films, only stiffening at 5 K","Neon films: classical stiffening, unlike helium's quantum switch","Elastic anomaly in neon films mirrors helium but stays classical"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000381,"raw_usage":{"total_tokens":2013,"prompt_tokens":930,"completion_tokens":1083,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":546,"completion_tokens_details":{"reasoning_tokens":993}},"tokens_in":546,"tokens_out":1083,"duration_ms":9648,"temperature":1.0,"reasoning_tokens":993,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T12:35:11.086558+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A decisive test is to vary the torsional oscillator's resonant frequency by about a factor of two at fixed neon coverage and see whether the dissipation peak stays at 5 K: if it moves with frequency, the peak is a resonance artifact; if it stays, the thermal-activation interpretation is supported.","supporting_citations":[{"cited_title":"Tao and A","cited_arxiv_id":null,"evidence_quote":"Supplies the helium-film elastic anomaly and the thermal activation model that the neon data are compared with and fitted to."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Origin of the localized-atom thermal activation picture used for helium and now neon."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Extends the model and provides the comparison critical coverage for helium on porous glass."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Gives the anelastic relaxation response functions used in the fitting."},{"cited_title":"Ny´ eki, A","cited_arxiv_id":null,"evidence_quote":"Provides heat-capacity evidence of two-dimensional phases of neon on graphite, the contrast for the disordered substrate."},{"cited_title":"Makiuchi, M","cited_arxiv_id":null,"evidence_quote":"Provides layer-by-layer growth and phase information on graphite, supporting the amorphous interpretation on porous glass."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the bulk solid neon shear modulus used to compare the film's effective stiffness."}],"review_version":1}