Surface states in crystals with low-index surfaces*
Wang Hui-Pinga), Tao Rui-Baoa),b)
       
(a) The schematic illustration of the lattice structure of a semi-infinite 2D crystal. (b)–(d) The dispersion relation of bulk states and edge states of a 2D crystal. Panels (b) and (c) show the absence of edge states when the symmetric hopping from the 2NN CPs is added. Panel (d) presents the existence of edge states when the hopping from the 2NN CPs is asymmetric. Here, (b) , (c) , and (d) t 2 = 0.4 t 1 and .