Axion Mie Theory of Electron Energy Loss Spectroscopy in Topological Insulators

Abstract

Electronic topological states of matter exhibit novel types of responses to electromagnetic fields. The response of strong topological insulators, for instance, is characterized by a so-called axion term in the electromagnetic Lagrangian which is ultimately due to the presence of topological surface states. Here we develop the axion Mie theory describing the electromagnetic response of spherical particles including an axion electromagnetic coupling at the surface of a particle. The approach includes arbitrary sources of fields, i.e., charge and current distributions. We derive an axion induced mixing of transverse magnetic and transverse electric modes which are experimentally detectable through small induced rotations of the field vectors. Contents

Optical response of a topological-insulator–quantum-dot hybrid interacting with a probe electric field

“…It is worth mentioning that the boundary conditions are perfectly consistent in relating field discontinuities at the interface with components of the fields which are continuous there. A number of magnetoelectric effects have been predicted on the basis of this theory [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57]. However, it has been experimentally verified only through the measurement of Kerr and Faraday angles at the surface of a strained HgTe 3D TI [58].…”