Effects of Impurity Adsorption on Topological Surface States of Bi2Te3

Abstract

Since its theoretical prediction, topological insulators (TIs) have been researched extensively from theoretical and experimental point of view. Integer quantum Hall systems being a topological phase were discovered even before the birth of TIs. But the current TI revolution has its roots in the formation of a topological states in the absence of an external magnetic field and its realization in 3 dimensions (3D). TI are the materials which are insulating in the bulk with metallic/conducting surface states which are robust against impurities until the time reversal symmetry is not broken. It is generally believed that non-magnetic impurities are harmless to the surface states compared to magnetic impurities which can generate backscattering channels and destroy surface states. In this thesis, we have discussed the possibility of some unusual disruption/modification when non-magnetic impurities interact with surface states of a 3D TI like Bi2Te3. Adsorption of (Rb, Ga, In and Au) on the surface of Bi2Te3 have been investigated using the first-principles, DFT based method focusing on the effect of these non-magnetic impurities on the topologically protected surface states. The bulk conduction band is moved downward with a significant Rashba splitting due to electron doping behavior with band modification details depending upon the adatom chemical character. Our study shows the robustness of the intrinsic spin-momentum coupled surface bands and emergence of a new bands, which could provide significant insight for developing novel spintronic devices.