Does Topology Enhance Thermoelectric Efficiency? A Case Study in Bismuthene

TL;DR

This study investigates how the topological properties of bismuthene influence its thermoelectric efficiency, revealing that edge states can both decrease and enhance the figure of merit depending on doping levels.

Contribution

It provides a detailed analysis of the impact of topological edge states on thermoelectric performance in bismuthene, combining band structure calculations with transport property evaluations.

Findings

Thermoelectric figure of merit drops in undoped topological bismuthene due to edge effects.

Edge states enhance ZT at high doping levels near the bulk band edges.

Topological properties can be leveraged to optimize thermoelectric efficiency in 2D materials.

Abstract

Two-dimensional (2D) bismuth (Bi) layer, known as bismuthene, exhibits $Z2$ topological bulk states due to large spin-orbit coupling that inverts the bands. Using the tight-binding method, we calculate the band structure of buckled bismuthene to understand its topological and trivial phases. We determine the thermoelectric properties for some considered phases, incorporating the edge states contribution, by using the linearized Boltzmann transport equation (BTE) with a constant relaxation time approximation. It is shown that the thermoelectric figure of merit, $ZT$, actually drops in undoped topological bismuthene due to the edge effects. Surprisingly, the topological edge states enhance $ZT$ at large doping with the Fermi energy near the bottom of bulk bands when bismuthene is nearly metallic.