Berry phase in cuprate superconductors
Bibliographic record
Abstract
The geometrical Berry phase is widely recognized as having profound implications for the properties of electronic systems. Over the last decade or so, the Berry phase has been essential to our understanding of new materials such as graphene and topological insulators. In general, a nontrivial Berry phase is a result of band crossing as in the case of a massless Dirac point. The Berry phase can be accessed in quantum oscillation measurements as it contributes to the phase mismatch of electrons in their cyclotron orbits. With their enigmatic pseudogap and superconducting phases, the cuprates are materials where the Berry phase is thus far unknown. Based on quantum oscillation data in the high-field normal state of underdoped cuprates, we determined the Berry phase contribution to the phase mismatch unambiguously in this family of materials. In the hole-doped materials ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}, {\mathrm{YBa}}_{2}{\mathrm{Cu}}_{4}{\mathrm{O}}_{8}$, and ${\mathrm{HgBa}}_{2}{\mathrm{CuO}}_{4+\ensuremath{\delta}}$, a trivial Berry phase of 0 $\mathrm{mod}(2\ensuremath{\pi}$) is systematically observed, while the electron-doped ${\mathrm{Nd}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{CuO}}_{4}$ exhibits a significant nonzero Berry phase of $1.4\ensuremath{\pi}$. Our results set significant constraints on the microscopic description of the high-field normal state and, in particular, do not support a nodal structure or broken time-reversal symmetry in the hole-doped compounds.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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".