Magnetic exchange driven proximity effect at a magnetic insulator / topological insulator (MI/TI) interface provides a rich playground for novel phenomena as well as a way to realize low energy dissipation quantum devices. Here we report a dramatic e
nhancement of proximity exchange coupling in the MI / magnetic-TI EuS / Sb$_{2-x}$V$_x$Te$_3$ hybrid heterostructure, where V doping is used to drive the TI (Sb$_{2}$Te$_3$) magnetic. We observe an artificial antiferromagnetic-like structure near the MI/TI interface, which may account for the enhanced proximity coupling. The interplay between the proximity effect and doping provides insights into controllable engineering of magnetic order using a hybrid heterostructure.
We present a theoretical investigation of the surface plasmon (SP) at the interface between topologically non-trivial cylindrical core and topological-trivial surrounding material, from the axion electrodynamics and modified constitutive relations. W
e find that the topological effect always leads to a red-shift of SP energy, while the energy red-shift decreases monotonically as core diameter decreases. A qualitative picture based on classical perturbation theory is given to explain these phenomena, from which we also infer that in order to enhance the shift, the difference between the inverse of dielectric constants of two materials shall be increased. We also find that the surrounding magnetic environment suppresses the topological effect. All these features can be well described by a simple ansatz surface wave, which is in good agreement with full electromagnetic eigenmodes. In addition, bulk plasmon energy at omega_{P}=17.5pm0.2eV for semiconducting Bi2Se3 nanoparticle is observed from high-resolution Electron Energy Loss Spectrum Image measurements.
We provide an analytical solution to study the near field optical effect of a core-shell nanostructure in proximity to a flat surface, within quasi-static approximation. The distribution of electrostatic potential and field enhancement in this comple
x geometry are obtained by solving a set of linear equations. This analytical result can be applied to a wide range of systems associated with near field optics and surface plasmon polaritons. As an illustration of the power of this technique, we study the field attenuation effect of oxidized shell in a silver tip in near field scanning microscope. The thickness of oxidized layer can be monitored by measuring the light intensity. In addition, we propose a novel method to detect local temperature with spatial resolution down to nm scale, based on a Ag-Au core-shell structure.
