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Optical properties and electronic structure of single crystals of LuAl 2 and YbAl 2 </mml:…

2000; American Physical Society; Volume: 61; Issue: 15 Linguagem: Inglês

10.1103/physrevb.61.10076

1095-3795

S. J. Lee, Seong Yeon Hong, I. R. Fisher, P. C. Canfield, B. N. Harmon, D. W. Lynch,

Advanced Chemical Physics Studies

The optical conductivities of single crystals of ${\mathrm{LuAl}}_{2}$ and ${\mathrm{YbAl}}_{2}$ were measured by spectroscopic ellipsometry in the energy range of $1.4--5.5\mathrm{eV}$ for ${\mathrm{LuAl}}_{2}$ and $1.4--5.2\mathrm{eV}$ for ${\mathrm{YbAl}}_{2}.$ The optical conductivity spectra of ${\mathrm{LuAl}}_{2}$ and ${\mathrm{YbAl}}_{2}$ show similar features except for a difference in magnitude. Both have peaks near $1.8--2.1\mathrm{eV}$ and broad shoulders between $3.0 \mathrm{and} 4.0\mathrm{eV}.$ The shoulder is weaker in ${\mathrm{YbAl}}_{2}.$ The band structure, density of states, and optical conductivity were calculated with the tight-binding linear muffin-tin orbital method in the atomic sphere approximation. The calculated optical conductivity with the inclusion of energy-dependent broadening agrees well with the experimental data. Oxidation effects on the surface of the sample were modeled using a three-phase model. The calculated optical conductivity of the clean surface is enhanced over that of the oxidized surface.