Strain-driven topological phase transitions and tunable topological states in the Bi₂Se₃ family.

Strain allows for a controlled manipulation of the topological order and Dirac states in three-dimensional Bi-chalcogenide topological insulators. Based on ab-initio density functional methods, we predict a universal phase diagram for the Bi₂Se₃ family. Under elastic strain these compounds present metallic, topological and trivial insulating phases. Furthermore, by strain engineering we built realistic topological homojunctions (THs) in Bi₂Se₃. We show how the topological interface states arising in such THs can be reversibly tuned along with their electron doping, spatial localization and mutual interaction. A TH contains the simplest topological interface, and hence constitutes the 'Hydrogen atom' of topological states of matter. Our findings show a route to tune the topological states within the field of straintronics.

[1] Strain effects in topological insulators: topological order and the emergence of switchable topological interface states in Sb₂Te₃/Bi₂Te₃ heterojunctions. H Aramberri, MC Muñoz, Phys. Rev. B 95, 205422 (2017).
[2] Strain-driven tunable topological states in Bi₂Se₃. H Aramberri, MC Muñoz, J. Phys. Mater. 1 (1), 015009 (2018).