Synergy of Rashba and Topological Effects for High-Performance Bismuth-Based Thermoelectrics

TL;DR

This paper introduces a novel design strategy for high-performance bismuth-based thermoelectrics by leveraging Rashba splitting and topological effects to improve band convergence and reduce thermal conductivity.

Contribution

It demonstrates a theoretical approach to enhance thermoelectric performance using Janus topological insulators with Rashba splitting and band inversion.

Findings

Achieved a peak zT of 2.82 in Janus Bi2Se2Te.

Enhanced power factor through Rashba-induced band convergence.

Suppressed lattice thermal conductivity via structural asymmetry.

Abstract

Band convergence is a key strategy for enhancing thermoelectric (TE) performance. Herein, we demonstrate a promising approach to enhance band convergence through inducing Rashba splitting in topological insulators. Theoretically designed Janus $\beta$-Bi$_2$Se$_2$Te and $\beta$-Bi$_2$Te$_2$Se exhibited inherent topological band inversion and Rashba splitting due to the strong spin-orbit coupling (SOC) with broken inversion symmetry. These characteristics synergistically improve band convergence, leading to a substantially enhanced power factor. Meanwhile, the Janus structural asymmetry suppresses lattice thermal conductivity. Consequently, Janus structures achieve boosted TE performance, especially for $\beta$-Bi$_2$Se$_2$Te, peaking figure of merit ($zT$) of 2.82. This work establishes a new framework for designing Janus topological compounds with high TE performance by the synergistic effect of Rashba splitting and band inversion.