Experimental and theoretical characterization of x-ray induced excitons, magnons, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>d</mml:mi><mml:mi>d</mml:mi></mml:mrow></mml:math> transitions in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>MoO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math> nanosheets
Bibliographic record
Abstract
The Mo $4d$ shell in the ground state of ${\mathrm{MoO}}_{3}$ is widely believed to be unoccupied. However, this assumption lacks clear experimental and theoretical corroboration. Using x-ray absorption and emission spectroscopy along with resonant inelastic x-ray scattering, we provide experimental evidence of two-dimensional ${\mathrm{MoO}}_{3}$ exhibiting enhanced many-body effects due to its reduced dimensionality. The observed phenomena include many-body effects such as $dd$ and spin-flip excitations, valence-hole and excited electron, and core-hole and excited electron bound excitonic states. Moreover, density functional theory and ligand field-based calculations were performed to investigate and interpret the experimental spectra. Considering that these many-body effects can only be observed by the interaction of x-ray photons with ${\mathrm{MoO}}_{3}$ if the $4d$ state is partially occupied, our experimental and theoretical approach clearly demonstrates a partial occupation of the Mo $4d$ state, refuting the assumption that the ground state is a $4{d}^{0}$ state. The Mo d occupancy is $4{d}^{3.36}$ and $4{d}^{3.53}$ determined with two different theoretical approaches (density functional theory and multiplet, respectively) and the computed spectra agree very well with our measurements further supporting this finding. Both the two- and three-dimensional samples exhibit strong core-hole effects that reduce the absorption onset at both the Mo ${M}_{2,3}$ and O $K$ edge. The band gap of the three-dimensional sample is experimentally found to be 3.1 \ifmmode\pm\else\textpm\fi{} 0.2 eV; however, for the two-dimensional material, strong many-body effects, even at the O $K$ edge, prevent an accurate determination of this value. The presence of these quasiparticles influences the band dispersions near the Fermi level, and thus has a key role in the performance of possible ${\mathrm{MoO}}_{3}$-based devices.
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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 | 0.004 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.002 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.003 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.097 | 0.002 |
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; both teacher heads agree on what is shown here.
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".