{"id":"fb4f1069-1a22-4daa-b476-ba52e6825088","arxiv_id":"2607.20904","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"Using ultrafast Lorentz electron microscopy, the authors directly imaged microwave-driven motion of a hybrid antiskyrmion/surface-skyrmion texture, observing nonlinear second-harmonic response and counterclockwise core rotation.","lead":"Using time-resolved Lorentz electron microscopy, the authors captured picosecond-scale microwave-driven motion of a hybrid antiskyrmion texture in a room-temperature magnet. The results open a real-space window on high-frequency spin-texture dynamics, showing nonlinear area oscillations and core rotations that simulations tie to the three-dimensional core geometry.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Rotational-sense claim lacks uncertainty on the signed-area metric; sign of χ may not be robust to noise in the centroid tracks.","rationale":"I read the paper in good faith: the UEM experiment is described in detail, the phase-locked stroboscopic scheme is physically plausible, and the micromagnetic simulations provide independent support for the hybrid-texture interpretation. The strongest claim, however, is specifically the common counterclockwise rotational sense of the two cores. The signed area χ in Eq. (2) is the only quantitative evidence for that sense, and the manuscript gives no uncertainty on χ. The reader's weakest assumption concerns the identification of the inner vortex contrast with the surface-skyrmion cores; that is a real systematic assumption, but it is supported by prior tomography and by the simulation's L-TEM contrast. The more decisive numerical gap is that the sign of χ could be within noise: the centroid tracks are noisy, only two harmonic components are retained, and the measurement window is short. A bootstrap or residual-resampling test is directly feasible with the deposited UEM-workflow code and would settle whether the CCW claim is statistically meaningful. This does not change the reader's conditional verdict, but it sharpens the condition: the paper should report uncertainty on χ or make the raw core-position series available for independent resampling.","tokens_in":13887,"tokens_out":10268,"duration_ms":97999,"concrete_test":"Bootstrap the signed area for the 4 GHz core trajectories: take the measured raw (unfiltered) core-position time series for both the antiskyrmion and surface-skyrmion cores, generate at least 10^4 resamples by adding residuals drawn from the measured per-frame residual distribution to the bandpass-filtered trajectory, recompute χ from Eq. (2) for each resample, and report the bootstrap 95% confidence interval for each core. If either interval crosses zero, the CCW rotational-sense claim is unsupported; if both intervals exclude zero by a clear margin, the concern is resolved. The same check should be repeated for the 5.25 GHz data in Extended Data Fig. 5.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central conclusion that both cores share a counterclockwise rotational sense rests entirely on the sign of χ defined in Eq. (2), evaluated on bandpass-filtered core trajectories in Fig. 3f. The paper reports point estimates only: no error bar, confidence interval, or bootstrap is given for χ. The raw centroid scatter and residual covariance envelopes shown in Fig. 3c-d are not propagated into the signed-area calculation. Because the trajectories are reconstructed from only the 4 GHz fundamental and 8 GHz second-harmonic components over 2.5 cycles, plausible residual fluctuations or a different filter bandwidth could alter the small-amplitude components and potentially flip the sign of the total χ. This is distinct from (though compounded by) the reader's concern that the inner vortex-like L-TEM contrast may not cleanly track the surface-skyrmion cores; even if that identification is granted, the rotational-sense claim is not quantitatively supported without uncertainty on χ.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports time-resolved Lorentz TEM (UEM) observations of a hybrid antiskyrmion/surface-skyrmion texture in (Fe,Ni,Pd)3P under 4 GHz and 5.25 GHz microwave excitation. Using stroboscopic phase-locked imaging, the authors measure the oscillating area, width, and height of the antiskyrmion and extract fundamental and second-harmonic components. They track the centroid of the antiskyrmion contour and the centroid of the inner vortex-like contrast (attributed to the projected surface-skyrmion cores), and from these trajectories compute a signed area χ (Eq. (2)) to claim that both cores rotate counterclockwise. Micromagnetic simulations (MuMax3) with literature parameters reproduce the area modulation and the counterclockwise rotation, and correlate the z-dependent signed area with the second derivative of the core cross-section area along thickness.","tokens_in":14032,"tokens_out":10426,"duration_ms":88271,"significance":"If the claims hold, this is a significant methodological advance: real-space, picosecond visualization of microwave-driven dynamics of an antiskyrmion and coexisting surface skyrmions, with evidence for a nonlinear (second-harmonic) response and a common rotational sense of distinct topological cores. The combination of experiment and simulation, together with publicly available analysis code, makes the work reproducible. The identification of a geometry-dependent rotational response (correlation with d2S_core/dz^2) provides a concrete, falsifiable hypothesis for future studies. The manuscript also demonstrates the capability of RF-controlled stroboscopic UEM for direct imaging of programmable spin-texture dynamics.","major_comments":[{"comment":"The stated time calibration is internally inconsistent. For 4 GHz excitation the period is 250 ps, so a phase increment of Δφ = 5° corresponds to 3.47 ps, not 13.9 ps; conversely, 13.9 ps corresponds to 20° at 4 GHz. The text also states 'Δφ = 1° ~ 2.7 ps', which would imply a ~1 GHz reference. Since all time axes, the 4/8 GHz bandpass filter, and the '2.5 cycles' window depend on this calibration, please clarify the reference frequency of the phase shifter, give the correct phase-to-time conversion, and reconcile the number of frames with the claimed 2.5 microwave cycles.","section":"Experimental setup / Fig. 2a caption"},{"comment":"The central claim that both cores rotate counterclockwise rests entirely on the sign of χ computed from bandpass-filtered trajectories containing only the 4 GHz and 8 GHz components, with no uncertainty or sensitivity analysis. The residual covariance envelopes in Fig. 3c-d are not propagated to χ, and only a single texture is analyzed. I request a bootstrap of the raw centroid measurements (or an equivalent resampling) and a stability test of the sign under variations of the filter bandwidth or the number of retained harmonics; if the sign is not robust, the claim should be weakened or presented as tentative.","section":"The core dynamics / Eq. (2) / Fig. 3f"},{"comment":"The inner vortex-like L-TEM contrast is identified as the projected superposition of the surface-skyrmion cores on the basis of refs 28, 40, 41, and its centroid is used to track the surface-skyrmion core. This identification is the experimental basis for the surface-skyrmion trajectory and the common-rotation claim. I ask the authors to re-validate it in this context, for example by quantifying the sensitivity of the white-dot centroid to the segmentation threshold and by comparing the tracked trajectory with the projected surface-skyrmion core position in the simulated L-TEM images.","section":"The core dynamics / Figs. 3a-b"},{"comment":"The claim that the z-dependent signed-area profile 'correlates more closely' with d2S_core/dz^2 than with Q is made by visual inspection of a single simulation. I request a quantitative correlation measure (e.g., Pearson or Spearman coefficient over z) and a discussion of how the comparison would be affected by the static-field mismatch (Bs=150 mT in the simulation vs 100 mT in the experiment) and by the simplified isolated-texture geometry.","section":"Micromagnetic simulation / Fig. 4f"}],"minor_comments":[{"comment":"The subscripts for the circular components are garbled (e.g., 'Cେେ୛,௡' and 'Cେ୛,௡'); please use 'C_CCW,n' and 'C_CW,n' throughout, and check that the definition of χ_n uses the correct absolute squares.","section":"Eq. (2) and Eq. (3)"},{"comment":"The caption states that the ribbon represents the residual standard-deviation envelope of the amplitudes and phases, but the bar charts show point estimates without explicit error bars; please clarify whether the residual envelope corresponds to a confidence interval for the extracted amplitude and phase values.","section":"Fig. 2e-g"},{"comment":"For the 5.25 GHz dataset, the sentence describing the ~69 nm displacement subtraction should clarify whether this is a constant offset or a time-dependent drift, and how the correction affects the computed χ.","section":"Methods / UEM Data Processing"},{"comment":"The statement 'Δφ = 1° ~ 2.7 ps' conflicts with the 4 GHz excitation; please correct or specify the reference frequency at which this conversion applies (see major comment).","section":"Fig. 1a caption"}],"recommendation":"major_revision","confidential_remarks":"The time-calibration inconsistency (13.9 ps for 5° at 4 GHz) is the most serious issue; if it is a typo or a reference-frequency subtlety, it is fixable, but it must be resolved before the quantitative frequency analysis can be trusted. The lack of uncertainty on the signed-area χ is the main statistical weakness. The paper's core methodological contribution is potentially strong and well suited to the journal, provided these load-bearing points are addressed."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"What you should know first: this paper's real advance is methodological. It shows that a laser-free, RF-stroboscopic UEM can image microwave-driven magnetic texture dynamics in real space with picosecond time steps. The specific observations for a hybrid antiskyrmion/surface-skyrmion texture — anisotropic area breathing, a second-harmonic response, and distinct core trajectories — are plausible and clearly presented. The simulations are a genuine strength: they use literature parameters, are not fitted to the measured dynamics, and reproduce the key experimental features, including the counterclockwise rotation and the larger response at 5.25 GHz. That is real evidence, not just a story.\n\nThe paper does what it claims. The picosecond area changes, the 4 GHz plus 8 GHz structure in the filtered traces, and the qualitative difference between the two core trajectories are all supported by the figures. The second-harmonic component is the most original physical observation, and the correlation with anisotropic confinement is reasonable. The writing is clean, the figures are legible, and the methods section is detailed enough to reproduce the analysis if the data were available.\n\nThe soft spots are real but not fatal. The central rotational-sense claim rests entirely on the signed-area metric chi, and there are no error bars, bootstrap intervals, or sensitivity checks on the sign. The stress-test note is fair: with only 2.5 cycles and a bandpass filter, residual noise or filter choice could change the small-amplitude components and potentially flip the sign of chi. The analysis is also performed on a single texture, so there is no demonstration of shot-to-shot or texture-to-texture reproducibility. Separately, the inner vortex-like contrast is identified as the surface-skyrmion projection based on prior work, not re-established here; that identification is reasonable but not airtight. Two smaller issues: the simulation uses a 150 mT static field while the experiment uses 100 mT, and the paper does not comment on the discrepancy; and the raw image series are not deposited, only the custom scripts, which limits independent verification. None of these undermines the qualitative conclusions, but they do mean the rotational-sense claim is conditional rather than settled.\n\nWho gets value from this: experimentalists working on UEM or Lorentz TEM, and the topological-spin-texture community. The paper deserves a serious referee. I would send it out, with instructions to the authors to add uncertainty on the signed-area metric, analyze more than one texture if possible, address the static-field discrepancy, and make at least a representative raw data sequence available.\n\nMy recommendation: engage with it; the method result is likely to be cited, and the physical claims are strengthenable rather than wrong.","headline":"A solid method demonstration of ultrafast Lorentz TEM for gigahertz spin-texture dynamics, with a believable but under-quantified rotational-sense claim.","tokens_in":14627,"tokens_out":1849,"would_cite":true,"duration_ms":19826,"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":"Microwave-driven antiskyrmion motion can be imaged in real space with picosecond resolution.","keywords":["antiskyrmions","surface skyrmions","hybrid topological spin textures","ultrafast electron microscopy","Lorentz transmission electron microscopy","microwave-driven spin dynamics","stroboscopic pump-probe","second-harmonic nonlinear response"],"falsifier":"Re-run the micromagnetic simulation of the hybrid texture with the surface-skyrmion caps removed, keeping the central antiskyrmion, and compute the Lorentz projection under the same 4 GHz drive; if a comparable inner vortex-like feature still appears and its centroid traces a counterclockwise loop, the paper's identification of that feature with the surface-skyrmion cores is falsified.","tokens_in":13684,"feed_emoji":"🌀","tokens_out":12268,"duration_ms":105367,"temperature":0.7,"pith_summary":"This paper aims to show that microwave-driven motion of a topological spin texture can be watched directly in real space rather than inferred only from spectra. Using phase-locked pulses of electrons in a Lorentz transmission electron microscope, the authors image a hybrid antiskyrmion—a central antiskyrmion capped by skyrmions at the surfaces—while a 4 GHz field deforms it. The images reveal that the antiskyrmion area oscillates at the drive frequency and at a second-harmonic component, a sign of nonlinear response, and that the two kinds of core follow different trajectories but rotate in the same counterclockwise sense. Micromagnetic simulations reproduce these features and tie the counterclockwise rotation to the bending of the three-dimensional core along the thickness. If the paper is right, ultrafast electron microscopy becomes a general real-space probe for high-frequency spin dynamics, and core geometry, not topological charge, shapes the rotation.","feed_headline":"Microwave pulses show antiskyrmion cores circling in sync","feed_subtitle":"Real-space electron snapshots capture skyrmion and antiskyrmion cores rotating the same direction.","key_machinery":"The central object is the hybrid antiskyrmion texture: a single spin structure whose interior is an antiskyrmion while the top and bottom surfaces host skyrmions, so that the projected Lorentz image shows a square antiskyrmion boundary plus an inner vortex-like dot. The argument is carried by the phase-locked, laser-free stroboscopic ultrafast electron microscopy measurement, in which the same radio-frequency source both chops the electron beam into 4 GHz (or 5.25 GHz) pulses and drives the sample through a phase shifter and frequency doubler; stepping the phase yields delay-time snapshots with roughly 2.7 ps per degree. The quantitative diagnostic is the signed area $\\chi = \\frac{1}{2}\\oint(x\\,dy - y\\,dx)$ of each core trajectory, which separates the motion into counterclockwise and clockwise circular components and fixes the net rotational sense. In the layer-resolved simulations, $\\chi(z)$ is compared with the topological charge $Q$ and the second derivative of the core cross-section area $d^2S_{\\mathrm{core}}/dz^2$; the curvature quantity, not $Q$, marks where the counterclockwise response is enhanced.","core_discovery":"On its own terms, the paper establishes that a hybrid antiskyrmion texture in (Fe0.63Ni0.3Pd0.07)3P responds to 4 GHz and 5.25 GHz microwaves with measurable, picosecond-scale real-space motion. The enclosed area of the antiskyrmion oscillates at the drive frequency and at its second harmonic, with the fundamental area change carried mainly by the height modulation and the second-harmonic change carried mainly by the width modulation. Tracking the two core features separately, the authors find that the central antiskyrmion core and the surface-skyrmion core trace different orbital shapes yet both rotate counterclockwise. Micromagnetic simulations reproduce the area oscillation, the common rotational sense, and the larger orbital amplitude at 5.25 GHz, and attribute the enhanced counterclockwise response to the local bending of the three-dimensional core iso-surface along the thickness rather than to the topological charge.","pith_inferences":["The authors do not test whether the synchronized counterclockwise sense persists as sample thickness changes; if it does, the common rotation would be a generic property of vertically connected hybrid textures rather than a feature of this specific material.","If three-dimensional imaging with picosecond resolution becomes possible, it should reveal a depth-dependent rotational sense, because the simulations show clockwise components that dephase and partially cancel in projection.","The link between the second-harmonic area response and the width modulation suggests a practical readout: the axis with weaker confinement could be identified by which dimension dominates the frequency-doubled signal."],"forward_implications":["The same microwave tone makes the central antiskyrmion and the surface-skyrmion cores rotate counterclockwise, so in a hybrid texture the mutual coupling, not the individual topological charge, sets the rotational sense.","The measured 8 GHz second-harmonic component means a single 4 GHz tone produces frequency-doubled deformation, a nonlinear response that could be used for frequency conversion.","Simulations place resonances near 4.70 and 5.13 GHz, close to the two experimental drive frequencies, so sweeping the drive should expose discrete modes of the individual hybrid texture rather than the higher-frequency crystal modes reported for antiskyrmion arrays.","The layer-resolved signed area tracks $d^2S_{\\mathrm{core}}/dz^2$ rather than $Q$, so core-geometry curvature along the thickness is the quantity that controls where strong counterclockwise rotation is generated."],"supporting_citations":[{"why":"Establishes the FNPP material, its room-temperature antiskyrmions, and the inner vortex-like L-TEM contrast assigned to surface spin-whirl cores.","marker":"[28]"},{"why":"Supplies the earlier antiskyrmion-crystal resonance frequencies that the paper compares with the lower individual-texture resonances found here.","marker":"[30]"},{"why":"Supplies the RF-controlled stroboscopic UEM scheme used to pulse the electron beam and phase-lock it to the microwave drive.","marker":"[35]"},{"why":"Validates the laser-free RF strip-line implementation that preserves the field-emission beam quality for L-TEM imaging.","marker":"[36]"},{"why":"Provides the micromagnetic basis for expecting surface skyrmions to cap the antiskyrmion near the surfaces.","marker":"[40]"},{"why":"Gives the electron-holographic tomographic confirmation of the three-dimensional hybrid texture used to interpret the white-dot contrast.","marker":"[41]"},{"why":"Supplies the transport-of-intensity equation method used to recover the in-plane magnetic induction maps shown in Figure 1.","marker":"[42]"},{"why":"Supplies the micromagnetic simulation code used to reproduce the area oscillation and core trajectories.","marker":"[43]"}],"fun_headline_variants":["Microwave-driven antiskyrmion and skyrmion cores spin in sync","Real-space microscopy shows skyrmion cores rotating in unison","Picosecond snapshots capture antiskyrmion and skyrmion core motion","Microwave pulses drive antiskyrmion and surface skyrmion cores in lockstep"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The result depends on the assumption that the inner vortex-like contrast seen in Lorentz images is produced by the surface-skyrmion cores and that its centroid follows their motion; if that contrast also contains contributions from the antiskyrmion boundary or from other depths, the claimed surface-skyrmion trajectory would be contaminated.","fun_headline_variants_meta":{"raw":{"variants":["Microwave-driven antiskyrmion and skyrmion cores spin in sync","Real-space microscopy shows skyrmion cores rotating in unison","Picosecond snapshots capture antiskyrmion and skyrmion core motion","Microwave pulses drive antiskyrmion and surface skyrmion cores in lockstep"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000657,"raw_usage":{"total_tokens":2986,"prompt_tokens":903,"completion_tokens":2083,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":519,"completion_tokens_details":{"reasoning_tokens":2002}},"tokens_in":519,"tokens_out":2083,"duration_ms":13503,"temperature":1.0,"reasoning_tokens":2002,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-15T15:31:54.318097+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Re-run the micromagnetic simulation of the hybrid texture with the surface-skyrmion caps removed, keeping the central antiskyrmion, and compute the Lorentz projection under the same 4 GHz drive; if a comparable inner vortex-like feature still appears and its centroid traces a counterclockwise loop, the paper's identification of that feature with the surface-skyrmion cores is falsified.","supporting_citations":[],"review_version":1}