Electronic structure of 9 quintuple layers Bi₂Se₃within Density Functional Theory

Bismuth Selenide (Bi2Se3) is a well-known 3D-type topological insulator. The interior part of this material is insulating, while its surface state is metallic which is protected by time-reversal symmetry. The experimental study of this material by varying its thickness reveals that the metallic surface state starts to appear at a minimum thickness of six Quintuple Layer (QL). This study was performed within the Density Functional Theory (DFT) in which a vacuum gap is added to the multilayer structure in order to capture the surface states of the material. While a previous study has explored the electronic structure of this material upto a thickness of 8 QL, a more detailed information of how the system evolves from this thickness to a fully bulk limit has not much been explored. With this motivation, we propose to calculate the electronic structure of this material with thickness of 9 QL. We perform the DFT calculation using Quantum Espresso (QE) package. Our results show that the band structure of this system reveals the surface metallic states with many additional bands as compared to those of thinner layer systems.