RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan.
Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan.
Nat Commun. 2016 Jul 20;7:12245. doi: 10.1038/ncomms12245.
Electrodynamic responses from three-dimensional topological insulators are characterized by the universal magnetoelectric term constituent of the Lagrangian formalism. The quantized magnetoelectric coupling, which is generally referred to as topological magnetoelectric effect, has been predicted to induce exotic phenomena including the universal low-energy magneto-optical effects. Here we report the experimental indication of the topological magnetoelectric effect, which is exemplified by magneto-optical Faraday and Kerr rotations in the quantum anomalous Hall states of magnetic topological insulator surfaces by terahertz magneto-optics. The universal relation composed of the observed Faraday and Kerr rotation angles but not of any material parameters (for example, dielectric constant and magnetic susceptibility) well exhibits the trajectory towards the fine structure constant in the quantized limit.
三维拓扑绝缘体的电动力学响应的特征在于拉格朗日形式主义的普遍电磁项组成部分。这种量子电磁耦合通常被称为拓扑电磁效应，已经预测会引起奇异现象，包括普遍的低能磁光效应。在这里，我们通过太赫兹磁光技术报告了拓扑电磁效应的实验迹象，这表现在磁性拓扑绝缘体表面的量子反常霍尔态中的磁光法拉第和克尔旋转。由观察到的法拉第和克尔旋转角度组成的普遍关系，但不包括任何材料参数（例如介电常数和磁导率），很好地展示了在量子极限下趋近精细结构常数的轨迹。
