Dynamics of charge current gratings generated in GaAs by ultrafast quantum interference control
Bibliographic record
Abstract
Ballistic charge current gratings are induced in GaAs at $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ by quantum interference of single- and two-photon absorption using noncollinearly incident 775 and $1550\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, $150\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$ pulses. First-order diffraction of time-delayed $830\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, $150\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$ probe pulses is used to observe carrier evolution for injected densities near ${10}^{17}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. The current grating forms electron and hole charge-density gratings during pumping, and because the pumping is uniform while the carrier density and hence electronic specific heat is not, a carrier temperature grating also forms. The peak diffraction efficiency from both grating types is only $\ensuremath{\sim}{10}^{\ensuremath{-}9}$. The temperature grating, with modulation amplitude $\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, decays through cooling in $\ensuremath{\sim}500\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$. Space-charge fields neutralize the electron and hole density gratings by the end of pumping, but nonetheless leave a neutral, electron-hole pair density grating with amplitude of $\ensuremath{\sim}{10}^{\ensuremath{-}3}$ of the injected carrier density. At the highest injected carrier densities, the pair grating amplitude builds on a few picosecond time scale before decaying by recombination and ambipolar diffusion with an $\ensuremath{\sim}15\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$ time constant. A model based on continuity equations for carrier density, momentum, and energy during ballistic and drift motion is used to help interpret the experimental data. Besides qualitatively confirming the above dynamics, the model suggests that the pair grating amplitude and evolution is determined by two factors: (1) the warping or nonparabolicity of the hole bands and (2) the transfer of some electrons from the $\ensuremath{\Gamma}$-valley electron-density grating to the $L$, $X$ conduction band valleys during excitation, and their subsequent return to the $\ensuremath{\Gamma}$ valley on a few picosecond time scale.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
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".