Shear-strain-mediated photoluminescence manipulation in two-dimensional transition metal dichalcogenides
Bibliographic record
Abstract
Abstract In two-dimensional transition metal dichalcogenides, normal strain can modulate electronic band structures, yet leaving the optical selection rules intact. In contrast, a shear strain can perturb the spin-valley locked band structures and possibly induce mixing of the spin subbands which in turn can transfer oscillator strength between spin-allowed bright and spin-forbidden dark excitons. Here, we report a novel scheme to manipulate photoluminescence (PL) in a monolayer WSe 2 -MoSe 2 lateral heterostructures, controlled by an external bending method in which strong out-of-plane shear strain (OSS) of up to 5.6% accompanies weak in-plane normal strain up to 0.72%. The spectra revealed a striking dependence on the bending direction that is stagnant in the negative (compressive) strain region and then rapidly changes with increasing positive (tensile) strain. The dependency of the PL signal under tensile bending was represented not only by the large energy shift ( > 40 meV) of the lowest excited states of both the WSe 2 and MoSe 2 monolayers, but also by the tendency to violate the optical selection rules that brightens (darkens) the excitons of the WSe 2 (MoSe 2 ) side. The analyses on the observed energy shifts and PL intensity changes confirm the different origins in compressive bending compared with tensile bending. The well-established band-anticrossing is identified to be affecting only the compressive deformation region. The spectral changes in the tensile region, on the other hand, originates mainly from the generation of an off-diagonal perturbation to a spin-specific Hamiltonian induced by OSS. The degree of spin-state mixing, which correlates precisely with the spin-flip coefficient of the theoretical model, is further represented by the OSS matrix elements, the spin splitting energy, and the shear deformation potential.
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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".