Stacking of charge-density waves in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mn>2</mml:mn> <mml:mi mathvariant="normal">H</mml:mi> <mml:mtext>−</mml:mtext> <mml:msub> <mml:mi>NbSe</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:math> bilayers
Bibliographic record
Abstract
We employ electronic-structure calculations to investigate the charge-density waves and periodic lattice distortions in bilayer <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mn>2</a:mn> <a:mi mathvariant="normal">H</a:mi> <a:mtext>−</a:mtext> <a:msub> <a:mi>NbSe</a:mi> <a:mn>2</a:mn> </a:msub> </a:math> . We demonstrate that the vertical stacking can give rise to a variety of patterns that may lower the symmetry of the charge-density waves exhibited separately by the two composing <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mn>1</c:mn> <c:mi mathvariant="normal">H</c:mi> <c:mtext>−</c:mtext> <c:msub> <c:mi>NbSe</c:mi> <c:mn>2</c:mn> </c:msub> </c:math> monolayers. The general tendency to a spontaneous symmetry breaking observed in the ground state and the first excited states is shown to originate from a non-negligible interlayer coupling. Simulated images for scanning tunneling microscopy as well as geometric structure factors show signatures of the different stacking orders. This may not only be useful to reinterpret past experiments on surfaces and thin films, but it may also be exploited to devise ad hoc experiments for the investigation of the stacking order in <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mn>2</e:mn> <e:mi mathvariant="normal">H</e:mi> <e:mtext>−</e:mtext> <e:msub> <e:mi>NbSe</e:mi> <e:mn>2</e:mn> </e:msub> </e:math> . We anticipate that our analysis not only applies to the <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"> <g:mn>2</g:mn> <g:mi mathvariant="normal">H</g:mi> <g:mtext>−</g:mtext> <g:msub> <g:mi>NbSe</g:mi> <g:mn>2</g:mn> </g:msub> </g:math> , but is also relevant for thin films and bulk, whose smallest centrosymmetric component is indeed the bilayer. Finally, our results illustrate clearly that the vertical stacking is not only important for 1T structures, as exemplified by the metal-to-insulator transition observed in <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"> <i:mn>1</i:mn> <i:mi mathvariant="normal">T</i:mi> <i:mtext>−</i:mtext> <i:msub> <i:mi>TaS</i:mi> <i:mn>2</i:mn> </i:msub> </i:math> , but seems to be a general feature of metallic layered transition metal dichalcogenides as well. Published by the American Physical Society 2024
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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 | 0.007 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.001 | 0.003 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.003 | 0.004 |
| Research integrity | 0.001 | 0.003 |
| Insufficient payload (model declined to judge) | 0.077 | 0.007 |
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".