Topological insulators are novel state of matter in which bulk is insulator and edges are gapless. How do we calculate these gapless states? I am reading the following PRL
Feng Liu and Katsunori Wakabayashi, Novel Topological Phase with a Zero Berry Curvature The pdf file is available here.
In this PRL they have plotted gapless states in figure.3 but they are not mentioning about how they plotted these states. Is there any simple model from which I can understand how to plot ribbon spectra of edges states (as they have done in this paper).
They are providing a Hamiltonian in last paragraph on page#1 from which I successfully plotted the energy band structure given in Figure.1 using MATLAB.