Topological cutoff frequency in a slab waveguide: Penetration length in topological insulator walls

TL;DR

This paper investigates electromagnetic wave propagation in a slab waveguide with topological insulator walls, revealing a topologically stable cutoff frequency and a method to measure surface state penetration length.

Contribution

It introduces the concept of a topological cutoff frequency in such waveguides and proposes a way to measure the penetration length of surface states in 3D topological insulators.

Findings

Identification of a topologically stable cutoff frequency.

Agreement of theoretical results with experimental data.

Method for measuring surface state penetration length.

Abstract

We study the propagation of electromagnetic (EM) waves in a slab-type waveguide which walls consist of three-dimensional topological insulator (3D TI). The results show that a cutoff frequency with topological stability limits the spectrum that propagates along the waveguide and are in agreement with experimental observations. Our approach also provides a way to measure the penetration length of surface metallic states in 3D TI.