Electron Spectroscopy of Collective Excitations in Superconductors
Notice bibliographique
Résumé
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-Tc 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 YBa2Cu3O7 (YBCO) and anisotropic plasmons in metallic YCr6Ge6 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 YCr6Ge6 sustain bulk plasmons in the UV regime (∼ 19 eV) with parabolic dispersion (q2). 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 Tc superconducting films and kagome crystals. Particularly, it can be shown that interfaces and surfaces drive a unique phononic response in high Tc 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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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».