  We carry out both the tight-binding model and the $ab\ initio$ to study the
layered silicene, the spin, valley, sublattice degrees of freedom are taken
into consider and the effects of electric field, magnetic field, and even the
light in finite frequency together with its interesting optical propertice,
which are all closely related to the spin-orbit coupling and Rashba coupling
and lead to the tunable phase transitions (between the nontrivial topological
phase which has nonzero Chern number or nonzero spin Chern number and the
trivial phase). An exotic quantum anomalous Hall insulator phase are found
which has nonzero spin Chern number and nonzero valley Chern number and as a
giant-application-potential spintronic and valleytronics in the two-ternimate
devices based on the monolayer silicene for the information transmission. In
fact, the gap-out action can be understanded by analyse the Dirac mass as well
as the Zeeman splitting or the external-field-induced symmetry-broken, and the
changes of gap has a general nonmonotone-variation characteristic under both
the effects of electron filed-induced Rashba-coupling $R_{2}(E_{\perp})$ and
the electron field-induced band gap, and the band inversion related to the
spin-orbit coupling which absorbs both the spin and orbital angular of momentum
may happen during this process. The quantized Hall/longitudinal conductivity
together with the optical conductivity are also explored, we see that even in
the quantum spin Hall phase without any magnetic field, the two-terminate
conductivity can be reduced to the value $e^{2}/h$ by controlling the helical
edge model, and it can be further reduced to $e^{2}/2h$ by applying the
magnetic field which similar to the graphene.
