Nearly perfect valley filter in silicene

Temperature effects on the conductance, spin-valley polarization and tunneling magnetoresistance of single magnetic silicene junctions

Magnetic silicene junctions are versatile structures with spin-valley polarization and magnetoresistive capabilities. Here, we investigate the temperature effects on the transport properties of single magnetic silicene junctions. We use the transfer matrix method and the Landauer-Büttiker formalism to calculate the transmittance, conductance, spin-valley polarization and tunneling magnetoresistance (TMR). We studied the case forT= 0 K, finding the specific parameters where the spin-valley polarization and the TMR reach optimized values. Regarding the temperature effects, we find that its impact is not the same on the different transport properties. In the case of the conductance, depending on the spin-valley configuration the resonant peaks disappear at different temperatures. The spin polarization persists at a considerable value up toT= 80 K, contrary to the valley polarization which is more susceptible to the temperature effects. In addition, a stepwise spin-valley polarization can be achieved at low temperature. The TMR is attenuated considerably as the temperature rises, decreasing more than two orders of magnitude afterT= 20 K. These findings indicate that in order to preserve the spin-valley polarization and magnetoresistive capabilities of magnetic silicene junctions is fundamental to modulate the temperature adequately.

Electrically controllable sudden reversals in spin and valley polarization in silicene

We study the spin and valley dependent transport in a silicene superlattice under the influence of a magnetic exchange field, a perpendicular electric field and a voltage potential. It is found that a gate-voltage-controllable fully spin and valley polarized current can be obtained in the proposed device, and the spin and valley polarizations are sensitive oscillatory functions of the voltage potential. In properly designed superlattice structure, the spin and valley polarizations can be reversed from −100% to 100% by a slight change in the external voltage potential. The energy dispersion relations of the superlattice structure are also investigated, which helps us to understand the effects of the superlattice structure. The switching of the spin direction and the valley of the tunneling electrons by a gate voltage enables new possibilities for spin or valley control in silicene-based spintronics and valleytronics.