Engineering of the Topological Surface States and Topological Dangling Bond States in the (0001) Surface of Bi2Se3 via Structural Distortion

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The (0001) surface band structure evolution of Bi2Se3 is studied for different broken symmetries in the top quintuple layer (QL) of 8QLs slab. Each surface electronic structure shows dangling bond states (DBS) irrespective of broken symmetries introduced by the surface termination or layer vacancy. The DBS become topological (TDBS) in the presence of spin–orbit coupling (SOC) effect, which form multiple Dirac cones (DC) at the Γ and M points in the conduction band due to Bi1 termination in top QL. For Bi1 and Se2 terminations, the contribution of p‐orbital of Bi2 atom to DBS in the gap is negligible. The DBS eliminates the topological state of Bi2Se3 for all broken symmetries except Se2 layer vacancy. The band structure with only Se2 and Se3 layer vacancies shows a narrow‐bandgap semiconducting nature with a small bandgap value of 0.18 eV and 0.08 eV, respectively. The DC feature is observed in vacant atomic layer configurations with SOC. The layer vacancies created by Bi atoms form a metallic state, whereas those produced by Se atoms form a narrow‐bandgap semiconducting state. The introduction of broken symmetries in Bi2Se3 can be utilized in the tuning of surface states and TDBS for possible technological applications.