Optical and transport properties and the structural identification of IrTe2

IrTe2 exhibits a structural phase transition at Ts∼280 K. Utilizing the density functional theory, we have simulated optical spectra above and below Ts. Simulated optical absorption spectra for a specific (5X) structure show great agreement with experimental data below Ts, which provides the structural identification of IrTe2 at low temperature. Comparison between experimental and calculated optical spectra also indicates that the Ir-Ir dimer formation governs the optical transition over the wide energy window of the low frequency part. The analysis of Fermi surfaces and band dispersions supports the effects of dimerization on the optical spectra at the low frequency region. The conductivity calculation based on the Boltzmann transport theory within the constant relaxation time approximation reveals that the dimensional reduction as well as the change of conducting plane takes place during the structural transition of IrTe2.