PbSn(CH₃)₂ and PbSn(C₂H)₂ Monolayers as Rashba-Effect-Induced Two-Dimensional Topological Insulators for Thermoelectric Applications: A First-Principles Investigation

The Rashba effect in two-dimensional (2D) topological insulators leads to a reduction in the lattice thermal conductivity and an enhancement in the Seebeck coefficient due to the formation of unique electronic states and increased band degeneracy. In this study, we investigate the electronic and thermal properties of the 2D topological insulators PbSn(CH 3 ) 2 and PbSn(C 2 H) 2 using first-principles calculations and Boltzmann transport theory. The results show that the PbSn(CH 3 ) 2 and PbSn(C 2 H) 2 monolayers exhibit extremely low lattice thermal conductivities of 0.0326 and 0.0667 W/mK at 500 K, respectively. As a result, the thermoelectric figures of merit ( ZT ) for PbSn(CH 3 ) 2 and PbSn(C 2 H) 2 reach values of 4.91 and 3.76, respectively, significantly surpassing those of 2D topological insulator materials without Rashba effects. These findings suggest that PbSn(CH 3 ) 2 and PbSn(C 2 H) 2 monolayers are promising candidates for thermoelectric applications.