Microwave Absorption in 2D Topological Insulators with a Developed Edge States Network

A 2D HgTe quantum well is analyzed based on the assumption that the width fluctuations convert the system to a random mixture of domains with positive and negative energy gaps. The borders between ordinary and topological insulator phases form a network of the edge states covering the entire sample. The optical transitions within the edge states yield a 2D absorption. The qualitative consideration is based on the model of optical intraedge transitions in curved edge states together with percolation arguments.