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Resonant Raman scattering in NaV2O5 as a probe of its electronic structure | | M.J.Konstantinovic
; Z.V.Popovic
; T.Ruf
; M.Cardona
; A.N.Vasil’ev
; M.Isobe
; Y.Ueda
; | | Date: |
16 Jul 1999 | | Journal: | phys. stat. sol. (b) 215, 661 (1999). | | Subject: | Strongly Correlated Electrons | cond-mat.str-el | | Abstract: | In order to investigate the origin of the phase transition observed in NaV$_2$O$_5$, as well as its electronic structure, we have measured Raman intensities as a function of the laser wavelength above and below the phase transition temperature. In the polarized Raman spectra at room temperature we observe resonant enhancement of the 969 $cm^{-1}$ phonon mode when the laser energy approaches 2.7 eV, presumably related to the (p-d) electron hopping band, $O_3$($p_y$)-V($d_{xy}$), at 3.2 eV. The 969 $cm^{-1}$ mode originates from the stretching vibrations along the c-axis involving the V-$O_1$ bonds. Since an ellipsometric determination of the dielectric function $epsilon_{cc}$ yields no structure in the 1.7 to 5.5 eV photon energy range, we conclude that plane bonds couple strongly with the apical oxygens leading to a large Raman efficiency. In the low-temperature Raman spectra, almost all modes that become active below the phase transition temperature T$_c$=34 K show resonant behavior. The most interesting ones, those at 66 and 106 $cm^{-1}$, possibly of magnetic origin, exhibit a resonant intensity enhancement, approximately by an order of magnitude, for laser photon energies around 1.85 eV with respect to 2.43 eV. This resonance effect may be associated with a weak absorption band around 2 eV. Finally, a destructive interference between the resonant and the nonresonant contribution to the Raman scattering amplitude (i.e. an antiresonance) is found in the spectra for most of the (bb) low-temperature modes. | | Source: | arXiv, cond-mat/9907237 | | Services: | Forum | Review | PDF | Favorites | |
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