Charge-ordering phase transition and order-disorder effects in the Raman spectra of NaV2O5
arXiv:cond-mat/0006408 · doi:10.1103/PhysRevB.63.100303
Abstract
In the ac polarized Raman spectra of NaV2O5 we have found anomalous phonon broadening, and an energy shift of the low-frequency mode as a function of the temperature. These effects are related to the breaking of translational symmetry, caused by electrical disorder that originates from the fluctuating nature of the V {4.5+} valence state of vanadium. The structural correlation length, obtained from comparisons between the measured and calculated Raman scattering spectra, diverges at T< 5 K, indicating the existence of the long-range charge order at very low temperatures, probably at T=0 K.
8 pages, 4 figures, new version, to appear in PRB