The quantum anomalous Hall effect (QAHE) hosts the dissipationless chiral edge states associated with the nonzero Chern number, providing potentially significant applications in future spintronics. The QAHE usually occurs in a two-dimensional (2D) system with time-reversal symmetry breaking. In this work, we propose that the QAHE can exist in three-dimensional (3D) ferromagnetic insulators. By imposing inversion symmetry, we develop the topological constraints dictating the appearance of 3D QAHE based on the parity analysis at the time-reversal invariant points in reciprocal space. Moreover, using first-principles calculations, we identify that 3D QAHE can be realized in a family of intrinsic ferromagnetic insulating oxides, including layered and non-layered compounds that share a centrosymmetric structure with space group $R\bar{3}m$ (No. 166). The Hall conductivity is quantized to be $-\frac{3e^2}{hc}$ with the lattice constant $c$ along $c$-axis. The chiral surface sheet states are clearly visible and uniquely distributed on the surfaces that are parallel to the magnetic moment. Our findings open a promising pathway to realize the QAHE in 3D ferromagnetic insulators.
National Synchrotron Radiation Laboratory, University of Science and Technology of China（中国科学技术大学国家同步辐射实验室）；MESA+ Institute for Nanotechnology, University of Twente（特温特大学MESA+纳米技术研究所）；School of Physics, Northwest University（西北大学物理学院）；Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所北京凝聚态物理国家研究中心）；National Research Center for Physical Sciences at Microscale, University of Science and Technology of China（中国科学技术大学微尺度物理科学国家研究中心）；Shaanxi Key Laboratory for Theoretical Physics Frontiers（陕西前沿物理理论重点实验室）；Institute of Solid State Physics, TU Wien（维也纳工业大学固体物理研究所）
Theory of the Spin Seebeck Effect at a Topological-Insulator/Ferromagnetic-Insulator Interface
自旋塞贝克效应是指相邻磁系统中热驱动自旋电流在金属中感应的电压信号。我们提出了一个理论的自旋塞贝克信号的情况下，支持的电压信号的导体是拓扑保护的二维表面态系统之间的界面铁磁绝缘体（FI）和拓扑绝缘体（TI）。我们的理论使用狄拉克模型的TI表面状态，并假设海森堡交换耦合TI准粒子和FI磁化。自旋Seebeck电压是由TI表面态在半无限热驱动FI表面散射非平衡磁振子粒子数引起的。我们的理论很容易推广到任何二维导体中的自旋塞贝克电压是交换耦合到表面的FI。使用Bi $_2$ Te $_3$和钇铁石榴石材料参数计算的表面态载流子密度依赖的信号强度与最近的实验是一致的。
Temperature dependence of the electronic structure and Fermi-surface reconstruction of Eu(1-x)Gd(x)O through the ferromagnetic metal-insulator transition
Magneto-optical investigation of the field-induced spin-glass insulator to ferromagnetic metallic transition of the bilayer manganite (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$
为了研究磁场驱动自旋玻璃绝缘体到铁磁金属的转变，我们测量了（$_{0.4}$ Pr $_{0.6}$）$_{1.2}$ Sr $_{1.8}$ Mn $_2$ O $_7$的磁光响应.磁场的应用恢复铁磁状态的电子结构的整体红移，增长的束缚载流子本地化与铁磁域，发展的赝能隙，软化的Mn-O的伸缩和弯曲模式，表明结构的变化。我们讨论了领域和温度引起的趋势的框架内的富冈Tokura全球电子相图图片，并建议控制无序附近的相边界可以用来调整磁介电响应。自旋玻璃绝缘体到铁磁金属转变的恢复也可以驱动（La $_{0.4}$ Pr $_{0.6}$）$_{1.2}$ Sr $_{1.8}$ Mn $_2$ O $_7$中的300 K颜色变化。
Determination of the spin Hall angle by the inverse spin Hall effect, device level ferromagnetic resonance, and spin torque ferromagnetic resonance: a comparison of methods
