Quantum Anomalous Hall Effects in Graphene from Proximity-Induced Uniform and Staggered Spin-Orbit and Exchange Coupling

• Published in: Physical review letters 2020-04, Vol.124 (13), p.136403-136403, Article 136403
• Main Authors: Högl, Petra, Frank, Tobias, Zollner, Klaus, Kochan, Denis, Gmitra, Martin, Fabian, Jaroslav
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Coupling; Density functional theory; Exchanging; Graphene; Ising model; Phase transitions; Quantum Hall effect
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.124.136403

We investigate an effective model of proximity modified graphene (or symmetrylike materials) with broken time-reversal symmetry. We predict the appearance of quantum anomalous Hall phases by computing bulk band gap and Chern numbers for benchmark combinations of system parameters. Allowing for staggered exchange field enables quantum anomalous Hall effect in flat graphene with Chern number C=1. We explicitly show edge states in zigzag and armchair nanoribbons and explore their localization behavior. Remarkably, the combination of staggered intrinsic spin-orbit and uniform exchange coupling gives topologically protected (unlike in time-reversal systems) pseudohelical states, whose spin is opposite in opposite zigzag edges. Rotating the magnetization from out of plane to in plane makes the system trivial, allowing us to control topological phase transitions. We also propose, using density functional theory, a material platform-graphene on Ising antiferromagnet MnPSe_{3}-to realize staggered exchange (pseudospin Zeeman) coupling.