Light-induced charge and spin Hall currents in materials with $C_4K$ symmetry
Bibliographic record
Abstract
Berry curvature, a momentum space property, can manifest itself in current responses. The well-known anomalous Hall effect in time-reversal-breaking systems arises from a Berry curvature monopole. In time-reversal-invariant materials, a second-order Hall conductivity emerges from a Berry curvature dipole. Recently, it has been shown that a Berry curvature quadrupole induces a third-order ac Hall response in systems that break time reversal ($K$) and a fourfold rotational ($C_{4}$) symmetry, while remaining invariant under the combination of the two ($C_{4}K$). In this letter, we demonstrate that incident light can induce a $\rm dc$ Hall current in such systems, driven by the Berry curvature quadrupole. We consider a combination of a static $\rm dc$ electric field and an ac light-induced electric field. We calculate the current perpendicular to both the static electric field and the fourfold axis. Remarkably, the induced current is generically spin-polarized. A net charge current appears for light that is linearly or elliptically polarized, but not for circular polarization. In contrast, the spin current remains unchanged when the polarization of light is varied. This allows for rich possibilities such as generating a spin current by shining circularly polarized light on an altermagnetic material. We demonstrate this physics using a two-dimensional toy model for altermagnets.
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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 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| 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".