Phuoc, T. V., Sellier, C., Janod, E. & Marin, C. (2008) Polarized reflectivity of beta-Sr0.17V2O5. Phys. Rev. B, 77 075123.
Added by: Laurent Cournède (2016-03-10 21:58:42)
|Type de référence: Article
Numéro d'identification (ISBN etc.): 1098-0121
Clé BibTeX: Phuoc2008
Voir tous les détails bibliographiques
Mots-clés: alpha'-nav2o5, beta-na0.33v2o5, bronzes, charge order, lattice-vibrations, peierls compound nav2o5, phase, spin
Créateurs: Janod, Marin, Phuoc, Sellier
Collection: Phys. Rev. B
Consultations : 15/664
Indice de consultation : 3%
Indice de popularité : 0.75%
In order to investigate phonon dynamics, infrared polarized reflectivity was measured along the b axis and on the low symmetry ac face of a monoclinic beta-Sr0.17V2O5 single crystal. Whereas 11 A(u) modes are expected along the b axis, only four broad and asymmetric modes are observed. Such a discrepancy with factor group analysis presumably results from the coupling of the phonons with an electronic background. Thus, both reflectivity and optical conductivity, obtained from Kramers-Kronig analysis, were fitted with Fano line shapes. In the ac face, almost all the 22 B-u modes predicted by the factor group analysis are observed. Reflectivity spectra are analyzed by using a tensor dispersion formula. To extract phonon parameters, including dipole moments, not predicted by group theory, the model requires us to measure the reflectivity for at least three polarizations. The assignement of high frequency phonon modes is made by comparing bond length and mode frequencies with alpha-' NaV2O5 and V2O5 and by using the dipole moment directions. Phonon modes assigned to V-O-V rungs stretching show unusually large dampings. We interpret these anomalous dampings as due to charge delocalization within V-O-V rungs. The mean Born effective charge tensors obtained from the model show a clear anisotropy in the ac plane.
Added by: Laurent Cournède