Edge states of zigzag boron nitride nanoribbons

Tight-binding (TB) calculation for zigzag boron nitride nanoribbons (ZBNNRs) is presented. The TB parameters are obtained so as to reproduce density functional calculation. The analytical expressions of boron (nitrogen) edge states that lie near the bottom (top) of conductance (valence) bands are given. The modification of the potential near the edge is found to be important in explaining the small energy dispersion of the edge states. The energy band gap of ZBNNR decreases with increasing ribbon width, which is explained by the edge potential. We also discuss the half metallicity for ZBNNR by considering the Hubbard-type Coulomb interaction.