Dielectric function in HgTe between 8 and 300°K

Reflectivity spectra of HgTe were measured in the spectral region from 80 to 600 cm^-1 at temperatures between 8 and 300^∘{}K. The wave numbers of the transverse-optical phonon ωTO=117 cm^-1 and longitudinal-optical phonon ωLO=132 cm^-1 at 8^∘{}K were determined. The total dielectric function including the interband Γ₈-Γ₈ contribution was analyzed. Plasmon-phonon dispersion diagrams were obtained. The theoretical analysis is compared with experimental results at all temperatures. Possible consequences of the adiabatic approximation breaking down in zero-gap semiconductors is examined. A new low-frequency mode is reported, its temperature dependence is given, and its origin is discussed from physicochemical arguments.