  Intrinsic contribution to the spin Hall effect in a two-dimensional silicene
is considered theoretically within the linear response theory and Green
function formalism. When an external voltage normal to the silicene plane is
applied, the spin Hall conductivity is shown to reveal a transition from the
spin Hall insulator phase at low voltages to the conventional insulator phase
at higher voltages. This transition resembles recently reported phase
transition in a bilayer graphene. The spin-orbit interaction responsible for
this transition in silicene is much stronger than in graphene, which should
make the transition observable experimentally.
