Enhancement of the Thermoelectric Figure of Merit in the Dirac Semimetal Cd$_{3}$As$_{2}$ by Band-Structure and -Filling Control

TL;DR

This study demonstrates enhanced thermoelectric performance in the topological Dirac semimetal Cd$_{3}$As$_{2}$ through alloying with Zn, achieving a figure of merit over 0.5 by tuning band filling and topology.

Contribution

It introduces a method to improve thermoelectric efficiency in topological semimetals via alloying, controlling band structure and topology for better performance.

Findings

Figure of merit exceeds 0.5 at specific alloy compositions.

Enhanced power factor at certain alloy ratios.

Suppressed thermal conductivity at higher alloy content.

Abstract

Topological materials attract a considerable research interest because of their characteristic band structure giving rise to various new phenomena in quantum physics. Beside this, they are tempting from a functional materials point of view: Topological materials bear potential for an enhanced thermoelectric efficiency because they possess the required ingredients, such as intermediate carrier concentrations, large mobilities, heavy elements etc. Against this background, this work reports an enhanced thermoelectric performance of the topological Dirac semimetal Cd$_{3}$As$_{2}$ upon alloying the trivial semiconductor Zn$_{3}$As$_{2}$. This allows to gain fine-tuned control over both the band filling and the band topology in Cd$_{3-x}$Zn$_{x}$As$_{2}$. As a result, the thermoelectric figure of merit exceeds 0.5 around $x = 0.6$ and $x = 1.2$ at elevated temperatures. The former is due to an enhancement of the power factor, while the latter is a consequence of a strong suppression of the thermal conductivity. In addition, in terms of first-principle band structure calculations, the thermopower in this system is theoretically evaluated, which suggests that the topological aspects of the band structure change when traversing $x = 1.2$.