One-dimensional thermoelectrics induced by Rashba spin-orbit coupling in two-dimensional BiSb monolayer

Rashba spin-orbit coupling (SOC) in low dimensional systems plays a leading role in carrier transport under external stimuli such as electric and thermal fields. Via the first-principles calculation combined with Boltzmann transport theory, we investigate the effect of Rashba SOC on the thermoelectric performance of two-dimensional (2D) bismuth antimony (BiSb) monolayer. We find that Rashba SOC significantly promotes the thermoelectric performance. The calculated ZT value with Rashba SOC is 0.32 at room temperature, which is almost two times higher than that in spin-degenerate case (0.18). The enhanced thermoelectric response is attributed to Rashba SOC induced one-dimensional-like density of states and a prolonged carrier lifetime in the 2D BiSb sheet. Furthermore, the high thermoelectric performance is also beneficial from low thermal conductivity because the internal electric field in the Rashba system introduces the anharmonicity of phonons in BiSb monolayer. Our work sheds new light on the design of high-performance thermoelectric devices or materials in the inversion-symmetry broken systems with Rashba spin-splitting.