Enhancement of the effective disorder potential and the thermopower in Na$_x$CoO$_2$ through the electron-phonon coupling

TL;DR

This paper investigates how electron-phonon interactions enhance disorder effects and thermopower in Na$_x$CoO$_2$, suggesting a pathway to improve thermoelectric material efficiency through lattice coupling and disorder engineering.

Contribution

It demonstrates that electron-phonon coupling cooperates with disorder to increase effective disorder potential, providing new insights into thermoelectric property enhancement in Na$_x$CoO$_2$.

Findings

Electron-phonon coupling enhances effective disorder potential.

The interplay allows for smaller disorder strengths in models.

Lattice coupling and disorder can be exploited to improve thermoelectric efficiency.

Abstract

The effects of an electron-phonon ($e$-ph) interaction on the thermoelectric properties of Na$_x$CoO$_2$ are analyzed. By means of dynamical mean field theory calculations we find that the $e$-ph coupling acts in a cooperative way with the disorder, enhancing the effective binary disorder potential strength on the Co sites, which stems from the presence or absence of a neighboring Na atom. Hence, the inclusion of the $e$-ph coupling allows us to assume smaller values of the binary disorder potential strength -- which for Na$_x$CoO$_2$ are in fact also more reasonable. More generally, we can conclude that the interplay between disorder effects and coupling to the lattice can be exploited to engineer more efficient thermoelectric materials.