Perfect spin and valley polarized quantum transport in twisted SiC nanoribbons

The edge magnetism of zigzag SiC nanoribbons in its ground state is half-metallic, but is competed by a non-half-metal state that is energetically extremely close. In this work, we propose and theoretically analyze two-probe transport junctions that overcome this difficulty so that perfect half-metal quantum transport is realized. When two zigzag SiC nanoribbons are connected by a C–Si–C–Si tetramer where the right ribbon is turned by 180° around the transport direction, 100% spin polarization with nearly perfect transmission is obtained due to perfect momentum k -matching across the transport junction. We show such a transport to be independent of the magnetic configurations of the two ribbons. A concomitant property is that 100% valley polarized charge transport is achieved. In principle, the structure of the proposed transport junction turns SiC nanoribbons into a promising, robust, and essentially perfect spin and valley filter. (paper)