Manipulation of Dirac Cone in Topological Insulator/Topological Insulator Heterostructure

One of the key challenges in the research of topological insulators (TIs) is to establish a means to intentionally manipulate Dirac fermions. While the chemical substitution is commonly applied to control the sign and filling of Dirac carriers, it inevitably introduces disorders and impurities into the crystal, leading to deterioration of Dirac carrier properties. Here, we have experimentally established a method free from such problems by fabricating TI/TI heterostructures. We grew n quintuple layers of Bi2Te3 on Bi2Se3 and visualized the evolution of the band structure with n by angle-resolved photoemission spectroscopy. While the topological Dirac cone surface state is heavily electron-doped for n = 0, the Dirac point moves toward the Fermi level on increasing n due to the charge transfer across the interface. Moreover, the original circular Fermi surface exhibits an intriguing hexagonal warping for n greater than equal to 3 due to the enhancement of the local spin-orbit coupling. The TI/TI heterostructure offers an additional degree of controllability to manipulate Dirac fermions in TIs and provides a promising platform to realize exotic topological phenomena.