Magnetized topological insulator multilayers
Chao Lei, Shu Chen, A. H. MacDonald
Abstract
Significance Topological insulators have Dirac cone surface states protected by time-reversal symmetry (TRS). Weak magnetic order in topological insulator thin films can lead to the quantum anomalous Hall effect (QAHE), which was first realized by magnetic doping of topological insulators to establish a fragile ferromagnetic state. Recent work has established <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">MnBi</mml:mi> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">Te</mml:mi> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> </mml:msub> </mml:math> as a structurally ordered magnetic topological insulator. We report on a theoretical study of superlattices formed from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">M</mml:mi> <mml:mi mathvariant="normal">n</mml:mi> <mml:mi mathvariant="normal">B</mml:mi> <mml:mi mathvariant="normal">i</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">T</mml:mi> <mml:mi mathvariant="normal">e</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> </mml:msub> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">Bi</mml:mi> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">Te</mml:mi> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msub> </mml:math> building blocks that employs a simplified model validated by ab initio density-functional theory. We use it to shed light on the dependence of the quantum anomalous Hall effect on film thickness, magnetic configuration, the stacking sequences of the van der Waals coupled building blocks, and bulk electronic structure.