We report the complex dielectric function along and perpendicular to the IrO2 planes in the layered perovskite Sr2IrO4 determined by spectroscopic ellipsometry in the spectral range from 12 meV to 6 eV. Thin high quality single crystals were stacked to measure the c-axis optical conductivity. In the phonon response we identified 10 infrared-active modes polarized within the basal plane and only four modes polarized along the c-axis, in full agreement with first-principle lattice dynamics calculations. We also observed a strong optical anisotropy in the near-infrared spectra arising from direct transitions between Ir 5d t2g Jeff = 1/2 and Jeff = 3/2 bands, which transition probability is highly suppressed for light polarized along the c-axis. The spectra are analyzed and discussed in terms of relativistic LSDA+U band structure calculations.
@article{arxiv.1602.06090,
title = {Optical anisotropy of the Jeff = 1/2 Mott insulator Sr2IrO4},
author = {D. Pröpper and A. N. Yaresko and M. Höppner and Y. Matiks and Y. -L. Mathis and T. Takayama and A. Matsumoto and H. Takagi and B. Keimer and A. V. Boris},
journal= {arXiv preprint arXiv:1602.06090},
year = {2016}
}