  We investigate the interplay between the edge and bulk states, induced by the
Rashba spin-orbit coupling, in a zigzag silicene nanoribbon in the presence of
an external electric field. The interplay can be divided into two kinds, one is
the interplay between the edge and bulk states with opposite velocities, and
the other is that with the same velocity direction. The former can open small
direct spin-dependent subgaps. A spin-polarized current can be generated in the
nanoribbon as the Fermi energy is in the subgaps. While the later can give rise
to the spin precession in the nanoribbon. Therefore, the zigzag silicene
nanoribbon can be used as an efficient spin filter and spin modulation device.
