Band-population effects and intraband magneto-optical properties of a many-valley semiconductor: PbTe

We have performed magnetoreflectivity experiments on $n$-PbTe epitaxial films using the Faraday configuration ($\overrightarrow{\mathrm{B}}\parallel \mathrm{}\left[111\right]\mathrm{}$) in the frequency range of 10-400 ${\mathrm{cm}}^{-1\mathrm{}}$ and in magnetic fields up to 14 T. Cyclotron-resonance structures and dielectric anomalies have been observed at frequencies between the TO and LO lattice modes of PbTe. We interpret our results using a free-carrier susceptibility derived within the framework of a linear-response theory. The Landau-level structure has been calculated according to the $\overrightarrow{\mathrm{k}}·\overrightarrow{\mathrm{p}}$ approach of Mitchell and Wallis. In the quantitative description of magnetoreflectivity spectra we take into account the magnetic-field-dependent occupation of the Landau states. Fitting our data we determine a set of band parameters for PbTe, which also successfully describe magneto-optical experiments of other authors.