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

Abstract

Infrared reflectance measurements have been carried on highly p-type Bi2Te3 crystals over the broad temperature range from 10 to 650 K and their response function investigated. An anomalous nonmonotonous temperature dependence of the plasma edge frequency is observed-with a pronounced redshift and blueshift that appear above and below room temperature, respectively. Such behavior is explained in terms of the temperature evolution of the free carrier optical weight N/m* given by particular temperature dependence of the total carrier concentration N (determined by transport measurements) and characteristic (optical) mass m*. The effective mass strongly varies from m* = 0.1m0 (m0 electron rest mass) at 10 K to m* = 0.5m0 respective m* = 0.9m0 at 650 K depending on the evaluating procedure. The interpretation is corroborated by complementary magnetotransport and magnetoreflectivity experiments.