Demonstration of surface transport in a hybrid Bi₂Se₃/Bi₂Te₃ heterostructure

In spite of much work on topological insulators (TIs), systematic experiments for TI/TI heterostructures remain absent. We grow a high quality heterostructure containing single quintuple layer (QL) of Bi₂Se₃ on 19 QLs of Bi₂Te₃ and compare its transport properties with 20 QLs Bi₂Se₃ and 20 QLs Bi₂Te₃. All three films are grown on insulating sapphire (0001) substrates by molecular beam epitaxy (MBE). In situ angle-resolved photoemission spectroscopy (ARPES) provides direct evidence that the surface state of 1 QL Bi₂Se₃/19 QLs Bi₂Te₃ heterostructure is similar to the surface state of the 20 QLs Bi₂Se₃ and different with that of the 20 QLs Bi₂Te₃. In ex situ transport measurements, the observed linear magnetoresistance (MR) and weak antilocalization (WAL) of the hybrid heterostructure are similar to that of the pure Bi₂Se₃ film and not the Bi₂Te₃ film. This suggests that the single Bi₂Se₃ layer on top of 19 QLs Bi₂Te₃ dominates its transport properties.