Abstract
We study ballistic transport of Dirac fermions through silicene barriers, of width d, with an exchange field M and metallic gates above them that provide tunable potentials of height U. Away from the Dirac point (DP), the spin- and valley-resolved conductances, as functions of U, exhibit resonances and close to it a pronounced dip that becomes a transport gap when an appropriate electric field Ez is applied. The charge conductance gc of such a junction changes from oscillatory to a monotonically decreasing function of d beyond a critical Ez. This change of gc can be used to realize electric-field-controlled switching. The field M splits each resonance of gc in two spin-resolved peaks. The spin ps and valley pv polarizations of the current near the DP increase with Ez or M and become nearly perfect above certain of their values. We also show that ps and pv can be inverted either by reversing the polarity of U or the direction of M. For two barriers, there is no splitting in gc when the fields M are in opposite directions. Most of these phenomena have no analogs in graphene.
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