Colossal phonon drag enhanced thermopower in lightly doped diamond

TL;DR

This study reveals that lightly doped diamond exhibits extraordinarily high thermopower due to weak phonon decay and strong electron-phonon interactions, surpassing previous records and providing new insights into thermoelectric transport.

Contribution

It introduces a fully self-consistent ab initio approach to analyze coupled electron-phonon transport, uncovering giant phonon drag effects in diamond.

Findings

Thermopower reaches ~100,000 μV/K at 100 K in doped diamond.

Weak anharmonic phonon decay enhances phonon drag effects.

Large thermoelectric power factors are observed.

Abstract

Diamond is one of the most studied materials because of its unique combination of remarkable electrical, mechanical, thermal and optical properties. Using a fully self-consistent ab initio theory of coupled electron-phonon transport, we reveal another striking behavior: a huge drag enhancement of the thermopower of lightly doped diamond. Thermopower values of around 100,000 microvolts per Kelvin are found at 100 K, significantly exceeding the highest previously measured value in the correlated metal FeSb2, and occurring at much higher temperatures. The enormous thermopower in diamond arises primarily from exceptionally weak anharmonic phonon decay around and below 100 K that facilitates efficient momentum exchange between charge carriers and phonons through electron-phonon interactions. Exceedingly large thermoelectric power factors are also identified. This work gives insights into the physics of the coupled electron-phonon system in solids and advances our understanding of thermoelectric transport in the regime of strong drag.