Ab initio study of adatom adsorption on topological insulator thin film

Recently topological insulator has attracted great attention due to its intriguing electronic and transport properties. Topological insulator has bulk energy gap but conducting surface states which are chiral with a linear energy-momentum relation. These surface states are robust against external perturbations as they are protected by the time reversal symmetry. We studied the electronic structure of topological insulator Bi$_{2}$Te$_{3}$ thin film and investigated how it is modified upon the adsorption of single atomic impurities using first-principles calculations. We chose nitrogen (N), oxygen (O), sodium (Na) and cobalt (Co) atoms to study their adsorption on top of Bi$_{2}$Te$_{3 }$surface. We investigated the effect of non-magnetic and magnetic impurities on the surface states, and the band splitting due to the inversion symmetry-breaking by the Rashba field.