Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Statut Confirmé
Domaines cond-mat
Date Lundi 21 Novembre 2011
Heure 10:30
Institut IMPMC
Salle salle de conférence, 4ème Etage, couloir 22-23
Nom de l'orateur Weber
Prenom de l'orateur Frank
Addresse email de l'orateur
Institution de l'orateur Karlsruher Institut für Technologie Institut für Festkörperphysik
Titre Phonon softening and charge density wave formation in nbse2 and tise2
Résumé We report [1] inelastic x-ray scattering measurements of the temperature dependence of phonon dispersion in the prototypical charge-density-wave (CDW) compounds NbSe2 and TiSe2. Surprisingly, acoustic phonons in NbSe2 soften to zero frequency and become overdamped over an extended region around the CDW wavevector. This extended phonon collapse is dramatically different from the sharp cusp in the phonon dispersion expected from Fermi surface nesting. Instead, our experiments combined with ab initio calculations, show that it is the wavevector dependence of the electron-phonon coupling that drives the CDW formation in NbSe2 and determines its periodicity. For TiSe2 [2], we found theoretically that the above described electron-phonon coupling scenario is able to stabilize a CDW ground state as well. Calculations of the lattice dynamical properties are in good agreement with our experimental results for the soft phonon dispersion and linewidth. A more detailed analysis of the calculations yield wavevector dependent matrix elements, strong enough to stabilize the CDW order in combination with an enhanced electronic joint density of states at the ordering wavevector. 1 F. Weber et al., Physical Review Letters 107 (10), 107403 (2011). 2 F. Weber, et al. (2011).
Numéro de preprint arXiv
Fichiers attachés
  • seminWEBER2011.pdf (150416 bytes) OPEN

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