HALL EFFECTS IN TOPOLOGICAL INSULATORS

Abstract

Topological Insulator (TI) belong to a new phase of matter where the topological property is protected by time reversal symmetry (TRS). TIs have long been question of great interest since they can provide a novel material platform where the surface states usually play an essential role to generate new topological phases, such as quantum anomalous Hall (QAH) effect after breaking TRS. This thesis reports on the QAH and SHE of TI thin films and broken symmetry topological phases for different classes of topological materials. Our works fall in four categories: (1) QAH effect in TI thin film, (2) QAH effect with tunable Chern number near a Z2 topological critical point. (3) Unconventional QAH effect of topological crystalline insulators. (4) Intrinsic SHE in TI thin film. In the first part of thesis, we comprehensively investigate the QAH effect in magnetically doped Bi2Se3 thin film with different magnetic structures. In the second and third parts of thesis, we propose a mechanism to realize QAH phase without the surface state involved. We take two material classes: Z2 TI TlBi(S$_{1-\delta}$Se$_\delta$)$_2$ and topological crystalline insulator Pb$_{1-x}$Sn$_x$Te/Pb$_{1-x}$Sn$_{x}$Se as examples, where both of them are tunable from trivial to non-trivial phases via chemical composition. Specifically, we demonstrate that the magnetically doped materials near topological critical points are candidates for high Chern number QAH insulators. Our proposal successfully reduces the necessary exchange coupling strength for a targeted Chern number where the QAH phase occurs even in the trivial side of the material. Finally, the intrinsic SHE in Bi2Se3 thin film are also discussed.