The optical properties of a spherical topological insulator embedded concentrically in a single-electron system consisting of a core–shell GaAs quantum dot are analyzed, when the system is under a uniform external magnetic field. The topological insulator’s magnetoelectric response is computed in the effective framework of $\theta$-electrodynamics, which allows analytical calculations for the induced electric and magnetic potentials by Green’s Function method. The GaAs Hamiltonian is constructed in the effective-mass approximation, and its corresponding Schrödinger equation is numerically solved through the Lagrange-mesh method. We compute the total absorption coefficients and refractive index changes given by the non-linear iterative density matrix formalism up to third order. Our results show that the presence of the magnetoelectric material causes new dipolar transitions otherwise not allowed. Also, an enhancement of the photon absorption is found when the incident light polarization is oriented parallel to the external magnetic field, in comparison with perpendicular polarization. Moreover, we report an appreciable blue shift in the optical functions when the values of the $\theta$-parameter are increased. These results can be useful for indirect experimental measures of the magnetoelectric polarizability which is proportional to the QED fine-structure constant $\alpha$.

当系统处于均匀的外部磁场下时，分析了同心地嵌入由核-壳GaAs量子点组成的单电子系统中的球形拓扑绝缘体的光学特性。拓扑绝缘子的磁电响应是在计算的有效框架下计算的。$\theta$-电动力学，可以通过格林函数方法对感应电势和磁势进行分析计算。GaAs哈密顿量是在有效质量近似下构造的，其对应的Schrödinger方程是通过拉格朗日网格法进行数值求解的。我们计算非线性迭代密度矩阵形式学给出的总吸收系数和折射率变化，直至三阶。我们的结果表明，磁电材料的存在会导致新的偶极跃迁，否则将不允许。另外，与垂直极化相比，当入射光极化平行于外部磁场定向时，发现光子吸收得到增强。此外，$\theta$-参数增加。这些结果可用于与QED精细结构常数成比例的磁电极化率的间接实验测量$\alpha$。