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) The energy spectrum of bulk states and edge states obtained in terms of the exact diagonalization method. The parameters are , t 2 = 0.75 t 1, t 3 = t 4 = 0.4 t 1, VA = 0.6 t 1, and VB = −0.9 t 1.