Simulation And Study On Electronic Structure And Electric Field Behavior Of Bi-based Low Dimensional Materials

Topological insulators are a new quantum phase of matter with exotic properties.They have many remarkable properties?such as dissipation less transport?and are most likely to be one of the key steps in quantum computing.However,their topological properties depend on their internal time inversion symmetry,so these properties are susceptible to various external conditions?such as impurities,defects,electric fields and so on?.Among them,because of the inevitable introduction of electric field environment in the application of materials,the influence of electric field on the topological properties is particularly important.In this paper,we will study the influence of external electric field environment on the electronic structure of topological insulators through computer simulation.In this paper,we had mainly studied the Bi-based low-dimensional materials by simulating the cell model and electronic structure of Bi_1-xSb_x,Bi₂Se₃,(Bi_0.5Sb_0.5)₂Se₃ and Bi₂Te₂Se with the first-principles calculations based on density functional theory.By comparing the simulation results with the experimental results,we have confirmed the reliability of these models.By comparing the cell model,band structure and density of states of Bi₂Se₃,(Bi_0.5Sb_0.5)₂Se₃ and Bi₂Te₂Se,we have analyzed the effects of Sb and Te atoms on the crystal structure and electronic properties of Bi₂Se₃.In this paper,we have also simulated the changes of band structures and the density of states of Bi_1-xSb_x,Bi₂Se₃,(Bi_0.5Sb_0.5)₂Se₃ and Bi₂Te₂Se in different electric fields with different intensities.It is found that with the increase of electric field's strength,these electronic structure will be affected to varying degrees:Bi_1-xSb_x has no resistance to the electric field and its topology completely disappears in the electric field;Comparing the energy band structures of Bi₂Se₃,(Bi_0.5Sb_0.5)₂Se₃ and Bi₂Te₂Se in electric field,It was found that Bi₂Se₃ is the most affected by the electric field,and its topological properties disappear rapidly with the increase of the electric field;(Bi_0.5Sb_0.5)₂Se₃ can retain non-trivial topological surface states in low electric field;The electronic structure of Bi₂Te₂Se is less affected by the electric field than the single QL model of Bi₂Se₃,but the topological property of Bi₂Te₂Se is easily affected by the electric field strength and gradually disappear with the increase of the electric field strength.