Högl Petra, Frank Tobias, Zollner Klaus, Kochan Denis, Gmitra Martin, Fabian Jaroslav
Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany.
Department of Theoretical Physics and Astrophysics, Pavol Jozef Šafárik University, 04001 Košice, Slovakia.
Phys Rev Lett. 2020 Apr 3;124(13):136403. 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.
我们研究了具有破时间反演对称性的近邻修饰石墨烯（或类对称材料）的有效模型。通过计算系统参数基准组合的体能带隙和陈数，我们预测了量子反常霍尔相的出现。引入交错交换场可使具有陈数(C = 1)的平面石墨烯中出现量子反常霍尔效应。我们明确展示了锯齿形和扶手椅形纳米带中的边缘态，并探究了它们的局域化行为。值得注意的是，交错本征自旋轨道和均匀交换耦合的组合给出了拓扑保护的（与时间反演系统不同）赝螺旋态，其自旋在相反的锯齿形边缘处相反。将磁化方向从平面外旋转到平面内会使系统变得平凡，从而使我们能够控制拓扑相变。我们还利用密度泛函理论提出了一个材料平台——在伊辛反铁磁体(MnPSe_3)上的石墨烯——来实现交错交换（赝自旋塞曼）耦合。
