Polarized infrared reflectivity measurements have been performed on single crystals of the spin-Peierls compound alpha'-NaV2O5 in the temperature range 20-300 K. Pronounced spectral features associated with the formation of the dimerized phase were detected both in the a- and b-polarizations (perpendicular and parallel to the spin-1/2 chains, respectively). The temperature dependence of a salient spectral line at 718 cm^-1 sharply rising below the transition temperature T_SP obeys a (1-T/T_SP)^(2beta) law with T_SP \simeq 34.3$K and beta \simeq 0.25. In addition, a continuum signal is observed in the whole temperature range in the a-polarized optical conductivity spectra. In order to interpret these results, calculations of the static dimerization and of the optical conductivity based on a mean-field and a dynamical treatment of the lattice respectively are proposed.
@article{arxiv.cond-mat/9801194,
title = {Study of spin-Peierls transition in alpha'--NaV2O5 by infrared reflectivity},
author = {D. Smirnov and P. Millet and J. Leotin and D. Poilblanc and J. Riera and D. Augier and P. Hansen},
journal= {arXiv preprint arXiv:cond-mat/9801194},
year = {2009}
}