Linear and ultrafast optical spectroscopy in the regime of the quantum Hall effect
Bibliographic record
Abstract
Abstract We review our optical experiments on two‐dimensional electron systems (2DES) of different mobilities, realized in modulation‐doped GaAs–AlGaAs single quantum wells, in quantizing magnetic fields. The carrier densities of the 2DESs could be tuned in a quite broad range between about 1 × 10 10 cm –2 and 2 × 10 11 cm –2 via gate electrodes. In photoluminescence (PL) and absorption experiments on 2DES with moderate mobility, at very low electron densities, we have observed the formation of negatively charged excitons. In these experiments, we could identify a dark triplet exciton, which is observable at temperatures below 1 K and for electron filling factors v < 1/3 i.e., in the fractional quantum Hall regime, only. In experiments where we have increased the density of the 2DES so that a uniform 2DES starts to form, we have found a strong energetic anomaly of the charged excitons in the vicinity of filling factor 1/3. The anomaly could be explained by a model, assuming that at very low temperatures localized charged excitons and a uniform Laughlin liquid coexist. Furthermore, we report on ultrafast optical experiments at the v = 1 quantum Hall state of a high‐mobility 2DES in a GaAs–AlGaAs single quantum well. By spectrally‐resolved four‐wave‐mixing experiments, we have investigated the coherent dynamics of photo‐excited electron–hole pairs and found extraordinarily long decoherence times for electrons, excited into the upper spin level, around v = 1 We attribute the observed faster decay of the dephasing time for v < 1 as compared to v > 1 presumably to the coherent coupling of the spin levels via spin waves. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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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 | 0.000 | 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) | 0.000 | 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 teacher head, 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".