First-principles Calculations On The Interactions Between Topological Insulator Surface States And The Adsorbed Magnetic Atoms

Topological insulator (TI) is a new quantum matter which is widely concerned by physicists. Because of the spin-orbit coupling interaction, the topological insulators has the metallic surface state and the insulative bulk state. It’s surface electronic state is determined by the topological structure of the electron states, protected by the time reversal symmetry, therefor, the robust surface quantum state can survive with impurities doping or defects. These interesting properties keep the importance of topological insulators in the field of spintronics and quantum computation. Correspondingly, it is of great interest to investigate the interactions of magnetics atoms on the surface of TIs. In this paper, we have systematically investigated the interactions between the surface states of TI and the magnetic adatom by first-principles calculations. The remainder of the thesis is organized as follows:Chapter1:Here we first introduce the history of topological insulators, such as the background, formation mechanism and basic properties. Then we introduced the basic theory on TI and highlight some representative research results previously achieved.Chapter2:Here we mainly introduce the methodology adopted in this paper.Chapter3:This Chapter presents the calculated results of the electronic properties of some representative three-dimensional TIs, such as Bi2Se3and Bi2Te3. Here we focused on the role of the spin-orbit coupling, the thickness of TI films, and the defects played in determining the topological surface states. Specifically, the formation energy of different defects on the Bi2Se3(111)/Bi2Te3(111) is calculated, in comparison with experiments.Chapter4:Following on chapter3, we systematically explored the interaction of magnetic adatom, Fe, on Bi2Te3(111) for substrate. In this section, different thickness(1QL and2QL) of Bi2Te3(111) pristine(FCC and HCP)/defected nanofilms were considered. Additionally, the band structures, density of states and STM images are respectively obtained to reveal the interacts of substrate and adatom. Importantly, we have also put much effort on calculating the magnetism of the adsorbent/substrate complex. It is found that the surface state of TI substrate can effectively modulate the magnetism of the adsorbed magnetic adatom.Chapter5:In summary. By means of first-principles calculations, we have investigated the electronic structures of both bulk TIs and the topological surface states of their nanofilms counterparts, particularly, we focused on the interactions of magnetic adatom on the TI surface. We found that the Fe adatom can strongly adsorb on both the pristine and defected Bi2Te3(111) surface, via the coupling of its d-orbital with the p-orbital of substrate, the surface state can significantly modulate the electronic surface and reduce the magnetism of the adsorbed Fe atom. It is expected that the present findings may play constructive role in high efficient catalysis design upon TIs.