Optical phonon drag and variable range hopping mechanisms of thermoelectric power generation in charge density wave system o-TaS$_{3}$}

TL;DR

This study investigates thermoelectric power in o-TaS3, revealing that optical phonon drag and variable range hopping are key mechanisms, with measurements spanning 10 K to 300 K showing characteristic charge density wave features.

Contribution

It demonstrates that optical phonon drag and localized carrier hopping are universal mechanisms in thermoelectric power generation in charge density wave systems.

Findings

Thermoelectric power peaks at around one-third to one-half of the transition temperature.

Sign change in thermoelectric power at low temperatures.

Optical phonon interactions and hopping conduction explain observed features.

Abstract

We have measured the thermoelectric power of charge density wave system $o$-TaS$_{3}$ in a wide temperature range between 10 K and 300 K. All features characteristic for charge density wave systems have been observed; strong increase below charge density transition temperature $T_{P}$, peak at $T_{M}\sim$1/2-1/3 $T_{P}$ and change of sign at lower temperatures. These features can be explained by two contributions; free carriers drag by the optical phonons with frequencies close to the density wave gap value in the peak region and above, and hopping of localized carriers of opposite charge to free carriers at low temperatures. We argue that these are common mechanisms of thermoelectric power generation in all charge density wave systems.