Magnon spectra of cuprates beyond spin wave theory
Bibliographic record
Abstract
The usual starting point for understanding magnons in cuprate antiferromagnets such as <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msub> <a:mi>La</a:mi> <a:mn>2</a:mn> </a:msub> <a:msub> <a:mi>CuO</a:mi> <a:mn>4</a:mn> </a:msub> </a:mrow> </a:math> is a spin model incorporating cyclic exchange, which descends from a one-band Hubbard model, and has parameters taken from fits based on non-interacting spin wave theory. Here we explore whether this provides a reliable description of experiment, using matrix product states (MPS) to calculate magnon spectra beyond spin wave theory. We find that analysis based on low orders of spin wave theory leads to systematic overestimates of exchange parameters, with corresponding errors in estimates of Hubbard <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mrow> <b:mi>t</b:mi> <b:mo>/</b:mo> <b:mi>U</b:mi> </b:mrow> </b:math> . Once these are corrected, the “standard” model provides a good account of magnon dispersion and lineshape in <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mrow> <c:msub> <c:mi>La</c:mi> <c:mn>2</c:mn> </c:msub> <c:msub> <c:mi>CuO</c:mi> <c:mn>4</c:mn> </c:msub> </c:mrow> </c:math> , but fails to fully capture the continuum observed at high energies. The extension of this analysis to <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:msub> <d:mi>CaCuO</d:mi> <d:mn>2</d:mn> </d:msub> </d:math> and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mrow> <e:msub> <e:mi>Sr</e:mi> <e:mn>2</e:mn> </e:msub> <e:msub> <e:mi>IrO</e:mi> <e:mn>4</e:mn> </e:msub> </e:mrow> </e:math> is also discussed.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 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".