We report optical (6 meV - 4 eV) properties of a boride superconductor ZrB12 (Tc = 6 K) in the normal state from 20 to 300 K measured on high-quality single crystals by a combination of reflectivity and ellipsometry. The Drude plasma frequency and interband optical conductivity calculated by self-consistent full-potential LMTO method agree well with experimental data. The Eliashberg function αtr2F(ω) extracted from optical spectra features two peaks at about 25 and 80 meV, in agreement with specific heat data. The total coupling constant is λtr=1.0±0.35. The low energy peak presumably corresponds to the displacement mode of Zr inside B24 cages, while the second one involves largely boron atoms. In addition to the usual narrowing of the Drude peak with cooling down, we observe an unexpected removal of about 10 % of the Drude spectral weight which is partially transferred to the region of the lowest-energy interband transition (∼ 1 eV). This effect may be caused by the delocalization of the metal ion from the center of the B24 cluster.
@article{arxiv.cond-mat/0609426,
title = {Optical properties and electronic structure of ZrB$_{12}$},
author = {J. Teyssier and A. B. Kuzmenko and D. van der Marel and F. Marsiglio and A. B. Liashchenko and V. Filippov and N. Shitsevalova},
journal= {arXiv preprint arXiv:cond-mat/0609426},
year = {2010}
}