Full-relativistic calculations of the SrTiO[sub 3] carrier effective masses and complex dielectric function.

We perform fully relativistic band-structure calculations for cubic SrTiO[sub 3], which are used to obtain carrier effective masses and the frequency behavior of its complex dielectric function ∈(ω). The obtained values and anisotropy of the carrier effective masses are shown to be highly influenced by the relativistic contributions. In order to evaluate the static dielectric constant, the low-frequency behavior of ∈(ω) is obtained by taking into account also the optical phonon contributions to the imaginary part of ∈(ω), adopting a simplified classical oscillator dispersion model. It is found that the phonon contribution leads to about 240 times (at T = 85 K) the value of the bare electronic contribution to the dielectric constant. The calculated temperature dependence of the dielectric constant is shown to be consistent with that observed in bulk SrTiO[sub 3] static permittivity measurements. [ABSTRACT FROM AUTHOR]