The dielectric function of alpha'NaV2O5 was measured with electric field along the a and b axes in the photon energy range 0.8-4.5 eV for temperatures down to 4K. We observe a pronounced decrease of the intensity of the 1 eV peak upon increasing temperature with an activation energy of about 25meV, indicating that a finite fraction of the rungs becomes occupied with two electrons while others are emptied as temperature increases. No appreciable shifts of peaks were found s in the valence state of individual V atoms at the phase transition is very small. A remarkable inflection of this temperature dependence at the phase transition at 34 K indicates that charge ordering is associated with the low temperature phase.
@article{arxiv.cond-mat/9911451,
title = {Low temperature ellipsometry of NaV2O5},
author = {C. Presura and D. van der Marel and A. Damascelli and R. K. Kremer},
journal= {arXiv preprint arXiv:cond-mat/9911451},
year = {2009}
}
Comments
Revisions in style and order of presentation. One new figure. In press in Physical Review B. REVTeX, 4 pages with 4 postscript figures