The effects of geometry, exchange and electric fields on transport properties of nonsymmetric T-shaped silicene nanoribbons

We propose two types of nonsymmetric T-shaped silicene nanoribbons that show peculiar spin transport properties. In type I and II T-shaped silicene nanoribbons, we modulate the overall conductance to one lead by changing the size of another lead. In type I T-shaped silicene nanoribbons, the conductance from L lead to R lead increases, while the conductance from L lead to T lead decreases with the size of R lead. A conductance gap near the Fermi energy is observed in the conductance from L lead to semiconducting T lead. Taking into account the exchange field, the near-perfect spin polarization can be acquired with ease at the semiconducting T lead. The spin polarization of each lead can be controlled by modulating the size of lead, electric field and exchange field. Similar properties are observed in type II T-shaped silicene nanoribbons. Thus the T-shaped silicene nanoribbons can serve as the important components of spin polarized nanodevice and nanocircuits.