Engineering quantum anomalous Hall phases with orbital and spin degrees of freedom

Abstract

Combining tight-binding models and first principles calculations, we investigate the quantum anomalous Hall (QAH) effect induced by intrinsic spin-orbit coupling (SOC) in buckled honeycomb lattice with sp orbitals in an external exchange field. Detailed analysis reveals that nontrivial topological properties can arise utilizing not only spin but also orbital degrees of freedom in the strong SOC limit, when the bands acquire non-zero Chern numbers upon undergoing the so-called orbital purification. As a prototype of a buckled honeycomb lattice with strong SOC we choose the Bi(111) bilayer, analyzing its topological properties in detail. In particular, we show the emergence of several QAH phases upon spin exchange of the Chern numbers as a function of SOC strength and magnitude of the exchange field. Interestingly, we observe that in one of such phases, namely, in the quantum spin Chern insulator phase, the quantized charge and spin Hall conductivities co-exist. We consider the possibility of tuning the SOC strength in Bi bilayer via alloying with isoelectronic Sb, and speculate that exotic properties could be expected in such an alloyed system owing to the competition of the topological properties of its constituents. Finally, we demonstrate that 3d dopants can be used to induce a sizeable exchange field in Bi(111) bilayer, resulting in non-trivial Chern insulator properties.

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• Topological Phases in Two-Dimensional Materials: A Brief Review
• Z2Pack: Numerical Implementation of Hybrid Wannier Centers for Identifying Topological Materials
• High-Chern-Number and High-Temperature Quantum Hall Effect without Landau Levels
• Surface orbitronics: new twists from orbital Rashba physics
• Quantum Anomalous Hall Effect in Time-Reversal-Symmetry Breaking Topological Insulators
• Functionalized Bismuth Films: Giant Gap Quantum Spin Hall and Valley-Polarized Quantum Anomalous Hall States
• Mixed topological semimetals driven by orbital complexity in two-dimensional ferromagnets
• Chern insulator in a hyperbolic lattice
• Quantum anomalous Hall effect in stable 1T-YN${}_2$ monolayer with a large nontrivial band gap and high Chern number
• In-Plane Magnetization Induced Quantum Anomalous Hall Effect in Atomic Crystals of Group-V Elements
• Spin and orbital transport in rare earth dichalcogenides: The case of EuS${}_2$
• Spin-orbit spillage as a measure of band inversion in insulators