Thermoelectric transport in a three-dimensional HgTe topological insulator

TL;DR

This study experimentally investigates the thermoelectric properties of strained HgTe thin films as a 3D topological insulator, highlighting phonon drag effects and electron-hole interactions affecting thermopower.

Contribution

It provides the first detailed experimental analysis of thermoelectric response in 3D HgTe topological insulators, comparing results with theoretical models.

Findings

Thermopower shows ambipolar behavior as Fermi energy shifts.

Thermopower mainly due to phonon drag contribution.

Seebeck coefficient affected by 2D electron - 3D hole scattering.

Abstract

The thermoelectric response of 80-nm-thick strained HgTe films of a three-dimensional topological insulator (3D TI) has been studied experimentally. An ambipolar thermopower is observed where the Fermi energy moves from conducting to the valence bulk band. The comparison between theory and experiment shows that the thermopower is mostly due to the phonon drag contribution. In the region where the 2D Dirac electrons coexist with bulk hole states, the Seebeck coefficient is modified due to 2D electron - 3D hole scattering.