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

Abstract

The optical conductivities of single crystals of ${\mathrm{ScAl}}_{3},$ ${\mathrm{LuAl}}_{3},$ and ${\mathrm{YbAl}}_{3}$ 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 ${\mathrm{ScAl}}_{3},$ and a weak shoulder is observed around at 2.8 eV for ${\mathrm{LuAl}}_{3}.$ Band structure, density of states, and optical conductivity were calculated using the full-potential linear augmented plane wave method. The calculated conductivity spectrum for ${\mathrm{ScAl}}_{3}$ shows peaks around at 2.7 and 4.3 eV. The distinctive feature of the optical conductivity for ${\mathrm{ScAl}}_{3}$ 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.