Flat band induced quantum criticality in a nonsuperconducting iron pnictide
Bibliographic record
Abstract
Flat electronic bands at the Fermi energy $({E}_{\mathrm{F}})$ can induce interaction-driven instabilities and further result in the emergence of a plethora of new quantum phases such as Mott insulators, ferromagnetism, fractional quantum Hall states even at high temperatures, and superconductivity. Except for flat bands in $f$-electron systems and special geometric lattices, however, the materials with quantum criticality induced by flat bands just at ${E}_{\mathrm{F}}$ remain elusive. Here, by using angle-resolved photoemission spectroscopy and band structure calculations, we present a comprehensive study of the low-energy electronic structure of a nonsuperconducting iron pnictide, $\mathrm{Ba}{({\mathrm{Fe}}_{1/3}{\mathrm{Co}}_{1/3}{\mathrm{Ni}}_{1/3})}_{2}{\mathrm{As}}_{2}$, which is a quantum-critical $3d$ transition metal alloy. We demonstrate the existence of a dispersionless flat band of ${t}_{2g}$ orbitals just at ${E}_{\mathrm{F}}$ which is responsible for quantum critical behaviors. Our findings will promote studies of emergent physics induced by flat bands, such as non-Fermi-liquid behaviors and quantum critical phenomena in $3d$ transition metals.
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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".