Optical rectification and shift currents in GaAs and GaP response: Below and above the band gap
Bibliographic record
Abstract
We present a full band structure scheme to calculate the electronic contribution to the second order susceptibility coefficient pertinent to optical rectification, ${\ensuremath{\chi}}_{2}^{abc}(\ensuremath{-}{\ensuremath{\omega}}_{\ensuremath{\sum}};{\ensuremath{\omega}}_{\ensuremath{\beta}},{\ensuremath{\omega}}_{\ensuremath{\gamma}})$ where ${\ensuremath{\omega}}_{\ensuremath{\sum}}\ensuremath{\approx}0$, within the independent particle approximation for the electron dynamics, and in the dipole limit. This allows us to determine the electronic response of a bulk semiconductor to a femtosecond optical pulse over a range of central frequencies, both below and above the band gap frequency. Particularly interesting is the limit ${\ensuremath{\chi}}_{2}^{abc}(0;\ensuremath{\omega},\ensuremath{-}\ensuremath{\omega})$. In addition to the usual near-dc interband rectification current, shift and injection currents, associated with actual divergences in ${\ensuremath{\chi}}_{2}^{abc}(0;\ensuremath{\omega},\ensuremath{-}\ensuremath{\omega})$, are taken into account. Calculations for GaAs and GaP, in which injection currents are forbidden, are performed. The band energies and matrix elements are computed with the full potential linearized augmented plane wave method. For frequencies above the band gap, and for typically available pulse widths, we demonstrate that the shift current dominates the current response, being approximately two orders of magnitude larger than the rectification current. For very narrow pulse widths, on the order of a femtosecond, the rectification current becomes comparable to the shift current.
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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) | 0.002 | 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".