Electron Spectroscopy of Collective Excitations in Superconductors
Bibliographic record
Abstract
Superconductor-based devices are key players for the development of a large variety of quantum applications including sensing and computing.Quantum applications operating above cryogenic temperatures is highly desired; this has reignited attention on the physics of high-T c superconductors.Although there has been significant progress in this research area, many questions remain unanswered including the role of phonons in electron-phonon interactions and transition temperatures [1].Furthermore, signal manipulation within a quantum system will require robust states which are insensitive to disturbances such as structural defects.There are indications that topological materials could provide a platform for realizing these states.Kagome superconductors have emerged as candidates for investigation of topological properties [2].Unveiling the electronic structure of kagome materials near the Fermi level is imperative.Assessing the collective behavior of valence electrons (plasmons) of Kagome materials offers opportunities to unveil the band structure near the Fermi energy, where topology bands and electronic correlations are actively driving physical effects.Spectroscopical studies of phonons and plasmons in superconductors are dominated by techniques assessing bulk properties.Advances in the generation of atom-wide monochromatic probes in electron microscopes allows the probing of collective excitations down to the deep mid-IR range with sub-5 meV energy resolution and high spatial sensitivity.These investigations can be performed in real and reciprocal spaces at different temperature regimes [3].We capitalize on these spectroscopy methodologies to study locally interface phonons in thin films of YBa 2 Cu 3 O 7 (YBCO) and anisotropic plasmons in metallic YCr 6 Ge 6 kagome crystals, thus uncovering unique behavior of collective excitations.In this talk, we will discuss the excitation of interface phonon modes at YBCO/LSAT interfaces.Phonon modes were probed at different locations within the film and near the LSAT boundary revealing strong phonon scattering variations.Bulk scattering was disentangled from surface contributions at the interface.Three main interface optical modes originating from mixed contributions of both YBCO and LSAT layers were identified.These interface modes are distinct from modes found in the bulk.Correlation between atomic structure and phonon properties unveiled local modes that are active near the interface.Furthermore, momentum-resolved EELS investigations reveal that YCr 6 Ge 6 sustain bulk plasmons in the UV regime ( 19 eV) with parabolic dispersion (q 2 ).An anisotropic bulk response was observed in terms of dispersion and damping in agreement with superconductivity transport measurements.The difference in plasmon energies between plasmons along (in and out-of-plane) directions in the long wavelength range (q 0) is explained in terms of electronic band structure.A reversal of this energy conditions is observed in the large q regime.Strong dispersion deviations were also observed suggesting that plasmon damping processes are active.Our spectroscopy results provide further understanding of collective excitations (i.e.phonons and plasmons) sustained in quantum materials such as high T c superconducting films and kagome crystals.Particularly, it can be shown that interfaces and surfaces drive a unique phononic response in high T c superconductors.Also, the plasmonic behavior of kagome metals shed light into their exotic electronic structure offering offer opportunities for further exploration of damping mechanisms assisted by exchange and correlation effects, which remain unexplored [4].
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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 | 0.000 | 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".