Tolerance and breakdown of topological protection in a disordered waveguide

Abstract

We consider a disordered waveguide consisting of trivial dielectric and non-trivial magnetically anisotropic material. A topologically protected edge mode appears owing to the broken time-reversal symmetry of the non-trivial lattice. While the edge mode maintains under other position and radius disorders, the protection is immediately broken by applying a radius disorder to the non-trivial lattice. This breakdown originates from donor and acceptor modes occupying the topological bandgap. Furthermore, via the calculation of the Bott index, we show that Anderson localization occurs as a metal conducting gap changes to a topological gap along with increasing disorders.