Nondiffusive electron transport in metals: A two-temperature Boltzmann transport equation analysis of thermoreflectance experiments
Bibliographic record
Abstract
We develop a theoretical framework based on the electron-phonon coupled Boltzmann transport equations (BTEs) for the interpretation of nondiffusive thermal conductivity measurements in metals made via frequency domain thermoreflectance (FDTR). The thermal conductivity of a bulk gold crystal was measured over a temperature range of 23--304 K as a function of FDTR's laser spot size. Our interpretation of these measurements by a two-temperature heat diffusion model finds that the thermal conductivity is suppressed when the laser spot size is comparable to electron mean free paths. Using a simplified spherical geometry that enables analytical solutions, we compare the two-temperature diffusion model with the coupled BTEs to identify a thermal conductivity suppression function. We also conclude that over the timescales of our experiment electron-phonon nonequilibrium is negligible, but that the length scale of heat deposition by hot electrons critically influences our interpretation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.004 | 0.001 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; both teacher heads agree on what is shown here.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".