Semi-metals as potential thermoelectric materials: case of HgTe

TL;DR

This study demonstrates that semimetal HgTe exhibits competitive thermoelectric properties, challenging the conventional belief that a bandgap is necessary for high thermoelectric efficiency, supported by both theoretical calculations and experimental data.

Contribution

The paper provides a comprehensive analysis of HgTe as a semimetal with high thermoelectric potential, combining ab initio calculations with experimental validation.

Findings

HgTe has a high thermoelectric power factor comparable to top materials.

The lattice thermal conductivity of HgTe is low, favoring thermoelectric performance.

Experimental measurements align well with theoretical predictions.

Abstract

The best thermoelectric materials are believed to be heavily doped semiconductors. The presence of a bandgap is assumed to be essential to achieve large thermoelectric power factor and figure of merit. In this work, we study HgTe as an example semimetal with competitive thermoelectric properties. We employ ab initio calculations with hybrid exchange-correlation functional to accurately describe the electronic band structure in conjunction with the Boltzmann Transport theory to investigate the electronic transport properties. We show that intrinsic HgTe, a semimetal with large disparity in its electron and hole masses, has a high thermoelectric power factor that is comparable to the best known thermoelectric materials. We also calculate the lattice thermal conductivity using first principles calculations and evaluate the overall figure of merit. Finally, we prepare semi-metallic HgTe samples and we characterize their transport properties. We show that our theoretical calculations agree well with the experimental data