Theory of thermoelectric effect in insulators

Yugo Onishi, Hiroki Isobe, Naoto Nagaosa

Published 2021-05-18, updated 2021-07-31Version 2

We propose a thermopolarization effect with a purely electronic origin, where the electric polarization $P$ is induced by the temperature gradient $\nabla T$. This is observable as a Seebeck effect in a finite-size system where the linear size $L$ is shorter than the Debye length $\lambda$, which characterizes the screening due to the thermal excitation of free carriers. The dual effect is the ac heat current induced by the time derivative of the electric field $E$. The Seebeck coefficient $S$ diverges as $\sim t_{\mathrm{asym}}/eT$ when the temperature $T$ goes to $0$, where $t_{\mathrm{asym}}$ represents the asymmetry of the conduction band and the valence band and $e$ is the elementary charge.