Tunable emergent topological surface states in Sb/Bi₂Te₃ and Bi₂Te₃/Sb thin-film heterostructures

Tuning the Dirac surface states of topological insulators (TIs) to achieve desirable surface properties is crucial for developing advanced TI-based electronics, but readily tunable TIs are limited. Our study of synthesized Sb/Bi₂Te₃ and the reversed Bi₂Te₃/Sb topological thin-film heterostructures, reported herein, illustrates a way to substantially broaden the class of tunable systems. In bulk form, Sb (a semimetal) and Bi₂Te₃ (an insulator) both host topological surface states with the invariant Z₂ = –1, whereas ultrathin Sb and Bi₂Te₃ films by themselves are fully gapped insulators. Photoemission band mappings, together with theoretical simulations of the band structure, reveal that in the single-layer Sb limit, the Sb/Bi₂Te₃ heterostructure supports emergent topological surface states strongly localized at the Sb surface. Further Sb coverage leads to a thickness-mediated evolution of the topological surface states along with a shift in the Dirac point energy. This heterostructure thus function as a TI with tunable surface properties controlled by Sb film thickness. These results and related data from the complementary system Bi₂Te₃/Sb will be presented.