Electron-phonon drag enhancement of transport properties from fully coupled \textit{ab initio} Boltzmann formalism

TL;DR

This paper uses fully coupled ab initio Boltzmann equations to show that electron-phonon mutual drag significantly enhances thermopower, mobility, and thermal conductivity in n-doped 3C-SiC, revealing new microscopic insights.

Contribution

It introduces a fully coupled ab initio approach to analyze electron-phonon interactions and demonstrates the significant impact of drag effects on transport properties.

Findings

Mutual electron-phonon drag enhances thermopower and phonon-dominated transport.

Drag boosts electron mobility, thermal conductivity, and Lorenz number.

Impurity scattering suppresses drag effects on conductivities, weakly affecting thermopower.

Abstract

We present a combined treatment of the non-equilibrium dynamics and transport of electrons and phonons by carrying out \textit{ab initio} calculations of the fully coupled electron and phonon Boltzmann transport equations. We find that the presence of mutual drag between the two carriers causes the thermopower to be enhanced and dominated by the transport of phonons, rather than electrons as in the traditional semiconductor picture. Drag also strongly boosts the intrinsic electron mobility, thermal conductivity and the Lorenz number. Impurity scattering is seen to suppress the drag-enhancement of the thermal and electrical conductivities, while having weak effects on the enhancement of the Lorenz number and thermopower. We demonstrate these effects in \textit{n}-doped 3C-SiC at room temperature, and explain their origins. This work establishes the roles of microscopic scattering mechanisms in the emergence of strong drag effects in the transport of the interacting electron-phonon gas.