The paper by Son, Cohen, and Louie explores the half-metallic properties of graphene nanoribbons (ZGNRs) under the influence of external electric fields. They predict that ZGNRs can exhibit complete spin polarization in electrical current due to the coexistence of metallic and insulating electronic states for electrons with different spins. The authors use first-principles calculations to show that applying homogeneous electric fields across the zigzag-shaped edges of ZGNRs can induce a half-metallic state, where one spin orientation is metallic and the other is insulating. This phenomenon is controlled by the external electric fields, which shift the energy levels of the localized edge states asymmetrically. The study also demonstrates that the half-metallic nature is robust even in the presence of defects, and that the spin direction determined by intrinsic spin-orbit interactions remains stable under strong transverse electric fields. The findings have implications for spintronics and the development of spin-based electronics using graphene-based materials.The paper by Son, Cohen, and Louie explores the half-metallic properties of graphene nanoribbons (ZGNRs) under the influence of external electric fields. They predict that ZGNRs can exhibit complete spin polarization in electrical current due to the coexistence of metallic and insulating electronic states for electrons with different spins. The authors use first-principles calculations to show that applying homogeneous electric fields across the zigzag-shaped edges of ZGNRs can induce a half-metallic state, where one spin orientation is metallic and the other is insulating. This phenomenon is controlled by the external electric fields, which shift the energy levels of the localized edge states asymmetrically. The study also demonstrates that the half-metallic nature is robust even in the presence of defects, and that the spin direction determined by intrinsic spin-orbit interactions remains stable under strong transverse electric fields. The findings have implications for spintronics and the development of spin-based electronics using graphene-based materials.