Robustness of quantum spin Hall effect-inspired edge modes depending on C6 symmetry in topological diffusion systems

Abstract

We investigate the robustness of a quantum spin Hall effect-inspired topological edge modes in a thermal diffusion system consisting of honeycomb-shaped structures. The robustness of the edge modes deteriorates because of the contributions of C6 symmetry breaking, thus resulting in the appearance of a large gap at the band-crossing point in the decay rate spectra. An interaction between more than two boundaries also leads to poor robustness, whereas strong C6 symmetry breaking improves the robustness deteriorated by such boundary interactions. Our study provides a guide for designing a robust edge mode with a desired decay rate in topological diffusion systems.