We study ballistic transport of Dirac fermions in silicene through arrays of
barriers, of width d, in the presence of an exchange field M and a tunable
potential of height U or depth βU. The spin- and valley-resolved
conductances as functions of U or M, exhibit resonances away from the Dirac
point (DP) and close to it a pronounced dip that becomes a gap when a critical
electric field Ezβ is applied. This gap widens by increasing the number of
barriers and can be used to realize electric field-controlled switching of the
current. The spin psβ and valley pvβ polarizations of the current near the
DP increase with Ezβ or M and can reach 100\% for certain of their values.
These field ranges widen significantly by increasing the number of barriers.
Also, psβ and pvβ oscillate nearly periodically with the separation between
barriers or wells and can be inverted by reversing M.Comment: 9 pages, 43 figures, to appear in PRB, figure resolutions reduced for
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