Optical properties and electronic structures of single crystallineRAl3(R=Sc,Yb, and Lu)

The optical conductivities of single crystals of ScAl 3 , LuAl 3 , and YbAl 3 were measured by spectroscopic ellipsometry in the energy range of 1.5-5.5 eV. The conductivity spectra of all show peaks between 1.5 and 2.0 eV originating from interband transitions. Two additional peaks around at 2.9 and 4.2 eV are observed for ScAl 3 , and a weak shoulder is observed around at 2.8 eV for LuAl 3 . Band structure, density of states, and optical conductivity were calculated using the full-potential linear augmented plane wave method. The calculated conductivity spectrum for ScAl 3 shows peaks around at 2.7 and 4.3 eV. The distinctive feature of the optical conductivity for ScAl 3 comes from the extraordinary large Sc d unoccupied density of states compared to those of Yb d and Lu d. Oxidation effects on the optical properties of the sample were studied using a three-phase model. The calculated optical conductivity of the clean surface using the three-phase model is larger than that of the oxidized surface.