Thermoelectric properties of two-dimensional topological insulators doped with nonmagnetic impurities

Abstract

We present a theoretical study on the thermoelectric properties of two-dimensional topological insulators (2DTIs) doped with nonmagnetic impurities. We develop a tractable model to calculate the electronic band structure without additional input parameters and to evaluate the thermoelectric properties of 2DTIs based on CdTe/HgTe quantum wells. We find that with increasing the doping concentration of nonmagnetic impurity, the edge states dominate the thermoelectric transport and the bulk-state conduction is largely suppressed. For typical sample parameters, the thermoelectric figure of merit ZT (a quantity used to characterize the conversion efficiency of a thermoelectric device between the heat and electricity) can be much larger than 1, which is a great advance over conventional thermoelectric materials. Furthermore, we show that with decreasing the 2DTI ribbon width or the Hall-bar width, ZT can be considerably further improved. These results indicate that the CdTe/HgTe 2DTIs doped with nonmagnetic impurities can be potentially applied as high-efficiency thermoelectric materials and devices.