Finite frequency magnetoelectric response of three dimensional Topological Insulators

TL;DR

This paper investigates the finite frequency magnetoelectric response of three-dimensional topological insulators, revealing new phenomena that occur at frequencies comparable to or larger than the surface gap, including in metallic states.

Contribution

It provides a theoretical description of the intrinsic finite frequency magnetoelectric response of topological insulators beyond the low-frequency limit, including metallic regimes.

Findings

Finite frequency response differs from the quantized low-frequency response.

New finite frequency phenomena of topological origin are predicted.

Response impacts observable physical quantities.

Abstract

Topological insulators with a time reversal symmetry breaking perturbation near the surface present a magnetoelectric response that is quantized when the frequency of the probing fields is much smaller than the surface gap induced by the perturbation. In this work we describe the intrinsic finite frequency magnetoelectric response of topological insulators for frequencies of the order and larger than the surface gap, including the experimentally relevant case where the system is metallic. This response affects physical observable quantities and will give rise to new finite frequency phenomena of intrinsic topological origin.