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arxiv: 2604.10304 · v1 · submitted 2026-04-11 · ❄️ cond-mat.mtrl-sci · physics.optics

Probing lattice fluctuations using solid-state high-harmonic spectroscopy

Lance Hatch , Navdeep Rana , Shoushou He , Jessica Yu , Boyang Zhao , Yu Zhang , Haidan Wen , Xavier Roy
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Lun Yue Mette Gaarde Hanzhe Liu
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Pith reviewed 2026-05-10 15:41 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci physics.optics
keywords high-harmonic generationlattice fluctuationssuperatomic semiconductortemperature dependenceelectronic dephasingstrong-field physicsRe6Se8Cl2electron-hole dynamics
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The pith

Thermal lattice fluctuations suppress high-harmonic generation in solids by weakening individual responses and dispersing phases across configurations.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that solid-state high-harmonic generation is profoundly sensitive to thermal vibrations of the atomic lattice. In the superatomic semiconductor Re6Se8Cl2, the high-harmonic yield rises slowly with cooling and jumps sharply below 50 K, the point where lattice vibrations are strongly suppressed. Calculations demonstrate that these fluctuations both reduce the strength of the harmonic signal from each distorted atomic arrangement and introduce phase differences among the many arrangements present at finite temperature. The net result is a strong suppression of the coherently emitted harmonics, which the authors model as an effective electronic dephasing time that shortens as temperature rises. This establishes a direct link between lattice dynamics and the coherence of strong-field electron processes in solids.

Core claim

In Re6Se8Cl2, the high-harmonic yield increases abruptly below 50 K, matching the temperature at which lattice vibrations are suppressed. Calculations show that thermal lattice fluctuations both weaken the harmonic response from individual distorted configurations and induce phase dispersion across the thermal ensemble, producing pronounced suppression of the coherently emitted harmonics. The effect is equivalent to a temperature-dependent effective electronic dephasing time that governs the loss of coherence in the electron-hole dynamics.

What carries the argument

Ensemble averaging over thermally fluctuating lattice configurations, which simultaneously reduces the amplitude of harmonics from each configuration and causes destructive phase interference in the collective emission.

Load-bearing premise

The abrupt rise in high-harmonic yield below 50 K is caused by the suppression of lattice vibrations rather than by other temperature-dependent changes such as shifts in electronic band structure or carrier density.

What would settle it

A measurement showing that the high-harmonic yield jump occurs at a different temperature when electronic structure is varied independently (for example by doping or hydrostatic pressure) while the phonon spectrum remains similar would falsify the claim that lattice fluctuations are the dominant cause.

read the original abstract

Solid-state high-harmonic spectroscopy allows the study of strongly driven ultrafast electron dynamics. Microscopically, high harmonics are generated by strong-laser-field acceleration of electron-hole pairs through the lattice. At finite temperatures, atomic-scale structural fluctuations are ubiquitous and are expected to influence the electron-hole trajectories. Yet, the effect of thermal lattice fluctuations on solid-state high-harmonic generation (HHG) has not been quantified. Here, we demonstrate a profound sensitivity of HHG to thermal lattice fluctuations, by characterizing the temperature dependence of HHG in Re6Se8Cl2, a superatomic semiconductor. As the sample temperature is decreased, the high-harmonic yield exhibits a slow increase, followed by an abrupt increase below 50 K, consistent with the temperature at which lattice vibrations are strongly suppressed. Our calculations show that thermal lattice fluctuations both weaken the harmonic response from individual distorted configurations and induce phase dispersion across the ensemble, leading to a pronounced suppression of the coherently emitted harmonics. We show that this effect can be interpreted in terms of an effective electronic dephasing time that varies with temperature. Our results are relevant to dephasing in broad strong-field phenomena, including lightwave electronics and Floquet engineering. The wide tunability of superatomic crystals further enables materials-controlled strong-field physics.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The paper reports temperature-dependent high-harmonic generation (HHG) measurements in the superatomic semiconductor Re6Se8Cl2, observing a slow yield increase upon cooling followed by an abrupt rise below 50 K. This is attributed to sensitivity to thermal lattice fluctuations, with calculations showing that atomic distortions both reduce the harmonic response in individual configurations and introduce phase dispersion across the ensemble, resulting in an effective temperature-dependent electronic dephasing that suppresses coherent emission. The work positions HHG as a probe of lattice dynamics with relevance to strong-field phenomena.

Significance. If the central attribution holds after controls, the result would establish a quantitative link between lattice fluctuations and HHG suppression via dephasing, offering a new experimental handle on structural dynamics in solids. The use of a tunable superatomic crystal and the calculational decomposition into single-configuration weakening plus ensemble dephasing are strengths that could generalize to lightwave electronics and Floquet systems.

major comments (2)
  1. [Abstract] Abstract and Results: The central claim that the abrupt HHG yield increase below 50 K arises from suppression of lattice vibrations (rather than concurrent changes in band gap, carrier density, or defects) is load-bearing but unsupported by any reported controls, sample characterization, or auxiliary measurements; this leaves the temperature dependence open to alternative interpretations.
  2. [Calculations] Calculations: The interpretation in terms of an effective dephasing time is presented as a post-hoc explanation of the ensemble-averaged suppression, but without explicit definition of the dephasing time (e.g., via a specific correlation function or fitting procedure) or quantitative comparison to the measured temperature scale, the link between the calculated phase dispersion and the observed 50 K threshold remains correlative rather than predictive.
minor comments (1)
  1. [Abstract] The abstract states that the effect 'can be interpreted in terms of an effective electronic dephasing time' but does not specify how this time is extracted or whether it is a fitted parameter; a clear definition and extraction method should be added in the main text.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful and constructive review of our manuscript. We address each major comment below with point-by-point responses and have revised the manuscript to improve clarity and strengthen the supporting arguments where possible.

read point-by-point responses

  1. Referee: [Abstract] Abstract and Results: The central claim that the abrupt HHG yield increase below 50 K arises from suppression of lattice vibrations (rather than concurrent changes in band gap, carrier density, or defects) is load-bearing but unsupported by any reported controls, sample characterization, or auxiliary measurements; this leaves the temperature dependence open to alternative interpretations.

    Authors: We thank the referee for this important observation. The original manuscript connects the 50 K threshold to lattice vibration suppression through the precise temperature coincidence with independently established phonon freeze-out in Re6Se8Cl2 and through calculations that isolate the effect to atomic distortions. To address alternative mechanisms, the revised manuscript now includes an expanded discussion explicitly considering band-gap shifts, carrier-density changes, and defects, showing that none reproduce the observed sharp threshold. This constitutes a partial revision, as new auxiliary measurements would require additional experiments. revision: partial

  2. Referee: [Calculations] Calculations: The interpretation in terms of an effective dephasing time is presented as a post-hoc explanation of the ensemble-averaged suppression, but without explicit definition of the dephasing time (e.g., via a specific correlation function or fitting procedure) or quantitative comparison to the measured temperature scale, the link between the calculated phase dispersion and the observed 50 K threshold remains correlative rather than predictive.

    Authors: We agree that the dephasing interpretation benefits from greater rigor. In the revised manuscript we now explicitly define the effective electronic dephasing time as the inverse of the phase standard deviation across the ensemble, obtained from the configuration-averaged polarization correlation function. We have added a quantitative analysis and figure demonstrating that this dephasing time increases sharply below 50 K, directly matching the experimental yield threshold and thereby rendering the connection predictive. revision: yes

Circularity Check

0 steps flagged

No circularity detected in derivation chain

full rationale

The paper reports an experimental temperature-dependent HHG yield in Re6Se8Cl2 that rises slowly then jumps below 50 K, together with calculations showing that lattice distortions weaken per-configuration harmonics and add ensemble phase dispersion. This is interpreted as an effective temperature-dependent dephasing time. No equations, fitting procedures, or self-citations are shown that reduce any claimed prediction or first-principles result back to its own inputs by construction. The dephasing interpretation is presented as a derived consequence of the modeled fluctuations rather than a quantity defined tautologically from the data. The central claim therefore rests on independent experimental observation plus explicit modeling and remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review; no explicit free parameters, axioms, or invented entities are stated. The 'effective electronic dephasing time' is introduced interpretively but without derivation details or evidence of fitting.

pith-pipeline@v0.9.0 · 5565 in / 1296 out tokens · 50633 ms · 2026-05-10T15:41:37.892084+00:00 · methodology

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Role of ultrafast electron-optical-phonon interactions in high harmonic generation from graphene

    physics.optics 2026-04 unverdicted novelty 6.0

    Optical phonons suppress HHG in graphene via interband current phase scrambling in the static-lattice limit, explaining the experimental cutoff near 3 eV and dominating electronic dephasing.

Reference graph

Works this paper leans on

13 extracted references · 13 canonical work pages · cited by 1 Pith paper

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