In-Plane Superfluid Density of Highly Underdoped YBa2Cu3O6+x
Bibliographic record
Abstract
The two most prominent states of matter in the phase diagram of the high temperature superconductors are the Mott insulator and d‐wave superconductor. Important clues for connecting the two states can be obtained by studying how the fundamental excitations evolve with doping. Using a breakthrough in the preparation of high purity YBa2Cu3O6+x crystals, we can tune into a regime of the underdoped cuprate phase diagram in which the transition temperature can be varied continuously between Tc = 25 K and zero, without changing cation disorder. A combination of microwave spectroscopy and measurements of the lower critical field Hc1 has been used to map out the temperature‐dependent superfluid density as a function of doping, with surprising results. The superfluid density becomes anomalously small in this doping range but shows no sign of a Kosterlitz‐Thouless transition. In addition, the temperature slope of the superfluid density is roughly proportional to Tc, suggesting a strong doping dependence of the charge‐current renormalization factor. In contrast to this, electron currents between the CuO2 layers are not renormalized, implying that the in‐plane quasiparticles are fundamentally different from the physical electrons that tunnel between layers.
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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".