Valley-polarized insulating states in zigzag silicene nanoribbons

Valley-polarized insulating states are found numerically in zigzag-edged silicene nanoribbons (ZSiNRs) because of the strong spin-orbit couplings and the spin-polarized electronic structures. We further investigate the effects of the valley-polarization on the transport and optical properties of ZSiNRs: it splits the degeneracy of ZSiNRs' conductance plateaus and offers valley-polarized transport channels; new optical activation modes appear for the singlet exciton states due to unequal cancellation of the contributions from different valleys.