Research On Topological Characteristics Of Superlattice Thin Films Composed By BiTe/SbTe

The bulk of a topological insulator can't conduct that it has an energy gap. At the same time, the topological insulator's surface can conduct that it's caused by spin-orbit coupling. As a new kind of the quantum material, the topological insulator has become one of the most important research fields in condensed matter physics. Superlattice structure is a film structure in Nano meter scale that their properties can be manually modulated, so the topological insulator with a superlattice structure is expected to realize the artificial modulation on the properties of the topological material. Therefore, the study of the topological insulator with a superlattice structure has great scientific significance in finding new physical phenomena and new topological insulator materials.In this thesis, based on first principle and using Materials Studio and VASP software,the energy band structures of some known topological insulators are calculated, including Bi2Te3 and Sb2Te3 films which have been verified by experiments, the simulation results coincide with these experiments. Based on these calculations, the superlattice film structures containing Bi2Te3 and Sb2Te3 are constructed and the energy bands are found to be dependent on the film structures in the topological insulator with a superlattice structure. The results show the surface states of the topological insulator films with a superlattice structure can be changed significantly when the crystal unit cell contains 3 to4 quintuple layers only. As more quintuple layers in the unit cell, the configuration has less impact on the surface state. In addition, the surface states of the topological insulator films with a superlattice structure are affected by the substrates when the unit cell contains 3quintuple layers, it indicates that we may adjust the surface states by different substrates.