Quantum Anomalous Hall Effect in Magnetic Doped Topological Insulators and Ferromagnetic Spin-Gapless Semiconductors -- A Perspective Review

TL;DR

This review discusses theoretical models and mechanisms for realizing the quantum anomalous Hall effect in magnetic topological insulators and spin-gapless semiconductors, emphasizing topological phase transitions driven by ferromagnetic exchange and spin-orbit coupling.

Contribution

It provides a comprehensive overview of three fundamental models for quantum anomalous Hall effect in various two-dimensional Dirac materials, highlighting symmetry constraints and phase transitions.

Findings

Models demonstrate how magnetic doping induces quantum anomalous Hall states.

Ferromagnetic exchange interaction drives topological phase transitions.

Symmetry considerations constrain the nature of mass terms in these models.

Abstract

Quantum anomalous Hall effect, with a trademark of dissipationless chiral edge states for electronics/spintronics transport applications, can be realized in materials with large spin-orbit coupling and strong intrinsic magnetization. After Haldane seminal proposal, several models have been presented to control/enhance the spin-orbit coupling and intrinsic magnetic exchange interaction. After brief introduction of Haldane model for spineless fermions, following three fundamental quantum anomalous Hall models are discussed in this perspective review: (i) low-energy effective four band model for magnetic-doped topological insulator (Bi,Sb)2Te3 thin films, (ii) four band tight-binding model for graphene with magnetic adatoms, and (iii) two (three) band spinfull tight-binding model for ferromagnetic spin-gapless semiconductors with honeycomb (kagome) lattice where ground state is intrinsically ferromagnetic. These models cover two-dimensional Dirac materials hosting spinless, spinful and spin-degenerate Dirac points where various mass terms open a band gap and lead to quantum anomalous Hall effect. With emphasize on the topological phase transition driven by ferromagnetic exchange interaction and its interplay with spin-orbit-coupling, we discuss various symmetry constraints on the nature of mass term and the materialization of these models. We hope this study will shed light on the fundamental theoretical perspectives of quantum anomalous Hall materials.