Topological Surface State of Bi₂Se₃ Modified by Physisorption of n‐Alkane

Abstract Recently, the interface between an organic molecular layer and a topological insulator (TI) surface (Org./TI interface) has been studied to explore the possibility of multifunctional TI devices with organic molecules. Nevertheless, understanding of the electronic structure of Org./TI interfaces is insufficient. Especially, little is known about physisorption systems, where the interaction between adsorbed molecules and topological surface state (TSS) is weak. Here, we discuss an ideal physisorption system of an n‐alkane molecule, n‐tetratertacontane (TTC), and prototypical TI, Bi₂Se₃, in which the interaction between the molecule and TSS is the weakest one possible. Angle‐resolved photoemission spectroscopy results show that the energy of the Dirac cone (DC) energy band decreases by approximately 60 meV when the TTC layer is formed on Bi₂Se₃. The amount of energy reduction is consistent with the reduction in vacuum level at the TTC/Bi₂Se₃ interface, valence states of Bi₂Se₃ and the core levels of Bi₂Se₃ observed by ultraviolet‐ and X‐ray photoemission spectroscopy. Therefore, no chemical interactions, such as charge transfer, occur at the TTC/Bi₂Se₃ interface, but only a redistribution of charge density on the Bi₂Se₃ surface occurs due to the Pauli repulsion between the electrons of the adsorbed TTC molecule and TSS.