Ab initio Prediction of Novel Induced Stacking Phase Transition in Intercalated Bi₂Se₃ Heterostructures: Implications on Thermoelectric Transport

In this work, we explore the role of metal intercalants in inducing a previously unknown structural phase transition in the 2D topological insulator Bi₂Se₃, from the conventional ABC bulk stacking to an AAA stacking configuration, and its impact on thermoelectric transport. We perform a comprehensive ab initio study of the preferred intercalant locations, their relative stabilities, and their impact on the stacking order of the ground state structural phase, for a wide variety of metallic and semi-metallic intercalant species. The resulting intercalant-driven phase transition, combined with the diverse doping and magnetic properties of the intercalants, opens new opportunities for tuning both the geometric and electronic properties of Bi₂Se₃ and potentially of other 2D vdW materials.

Specifically, we investigate the impact of the intercalant-induced phase transition both on the lattice thermal conductivity via phonon-phonon scattering processes and on the thermopower via electron-phonon scattering processes. Furthermore, by strategically combining intercalant species with different doping behaviors, we demonstrate how the thermopower can be tuned while keeping the material near the stacking phase transition. Finally, we examine the interplay between our new stacking phase transition, the magnetic properties of the intercalants, and Bi₂Se₃’s topological surface states, and explore the potential to tune the stacking of near-critically intercalated Bi₂Se₃ through strain.