Estudo de efeito spin-orbita na adsorção de Bi em superfícies de Si(111)

Abstract

This work consists on a deep analysis through ab initio of Bi/Si(111) surfaces in order to characterize magnetism, band and topological properties. Initially, we did a detailed review of the theoretical bases for characterization of topological systems and the Densty Functional Theory (DFT). It’s worth mentioning that in the review of the topological insulation characterization methods, we start from the fundamental concepts presented by M.V Berry going to the methods the Wannier functions and parity. With such tools in hand, we began our studies with ab initio calculations of the bilayer of Bi, characterizing it topologically through parity, thus we verify that the topological properties of the sheet are given by it’s parity in point M and not point r, as proposed in bibliography. We also perform the evolution of the Wannier Charge Centers for the bilayer with the intention of comparing the results between methods. The second step consists on the study of the stability of Bi’s adsorption in Si(111)y/3 x v^3 including the spin orbit coupling, thus confirming that the Milkstool Structure is the most stable structure as predicted by the calculation without SO coupling and more than that, the Spin-Orbit increases the energy difference between Milkstool and concurrent structures. Later on, we perfom band structure calculations through DFT, showing that SO coupling is little relevant in Milktool band structures calculations. Finally, we work on different Si-(111) structures and conclude that Bi layers do have strong interaction with the Si layers, displaying metallic states of Fermi level.