Crossover of Three-Dimensional Topological Insulator of Bi2Se3 to the Two-Dimensional Limit

Understand

Bi2Se3 is theoretically predicted1 2and experimentally observed2,3 to be a three dimensional topological insulator.

• For possible applications, it is important to understand the electronic structure of the planar device.
• In this work, thickness dependent band structure of molecular beam epitaxy grown ultrathin films of Bi2Se3 is investigated by in situ angle-resolved photoemission spectroscopy.
• An energy gap is observed for the first time in the topologically protected metallic surface states of bulk Bi2Se3 below the thickness of six quintuple layers, due to the coupling between the surface states from two opposite surfaces of the Bi2Se3 film.