Anomalous temperature dependence of the effective mass in p -type Bi2Te3

Infrared reflectance measurements have been carried on highly $p$-type ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ crystals over the broad temperature range from 10 to 650 K and their response function investigated. An anomalous nonmonotonous dependence of plasma edge frequency is observed---with a pronounced redshift blueshift that appear above below room temperature, respectively. Such behavior explained in terms evolution free carrier optical weight $N/{m}^{*}$ given by particular total concentration $N$ (determined transport measurements) characteristic (optical) mass ${m}^{*}$. The effective strongly varies ${m}^{*}=0.1{m}_{0}$ (${m}_{0}$ electron rest mass) at ${m}^{*}=0.5{m}_{0}$ respective ${m}^{*}=0.9{m}_{0}$ depending evaluating procedure. interpretation corroborated complementary magnetotransport magnetoreflectivity experiments.