Controllable spin filtering and half-metallicity in β12-borophene nanoribbons

The experimental observation of the Dirac fermion states in beta(12)-borophene sheets and the discovery of their novel topological properties have made them a promising candidate for spintronic applications. Here, by combining the nonequilibrium Green's function (NEGF) and tight-binding (TB) approximations, we study the charge and spin transport properties through a beta(12)-borophene nanoribbon (BNR) with different edge shapes. We show that for BNR exposed to a nonlocal exchange magnetic field, the spin filtering occurs so that the spin direction of transmitted electrons could be controlled by adjusting the energy of incoming electrons with the help of an external backgate voltage. It is found that an armchair BNR (ABNR) in the simultaneous presence of a transverse electric field and a nonlocal exchange field acquires half-metallic properties. The influence of local exchange fields is evaluated by exposing the edges of BNRs to ferromagnetic strips with parallel and antiparallel configurations. Our findings show that the edge manipulations in BNRs lead to the emergence of giant magnetoresistance and a perfect spin filter. Finally, we study the effects of edge vacancies and Anderson disorder on the spin-dependent conductance of an ABNR and find that the perfect spin polarization is not destroyed in the presence of Anderson disorder and various single vacancies. Our results reveal the outstanding spin transport properties of ABNRs for future spintronic devices.