Spin-Dependent Electronic Properties of Bilayer α‑Graphyne Zigzag Nanoribbons: A Density Functional Theory Study

Graphyne-based nanostructures have attracted growing interest due to their unique electronic and mechanical properties arising from a combination of sp and sp² hybridized carbon atoms. Recent advances have enabled the synthesis of various graphyne members, including few-layer films, quantum dots, and nanoribbons, opening new possibilities for nanoscale applications. In this work, we present a first-principles investigation of the spin-dependent structural and electronic properties of bilayer zigzag nanoribbons derived from the α-graphyne lattice. Four stacking arrangements (AA, Ab, AB-α, and AB-β) were considered, all of which result in nonplanar geometries. We demonstrate that bilayer α-graphyne zigzag nanoribbons exhibit a distinct spin-dependent behavior not observed in graphene-based counterparts, where nonplanar geometries preserve and even enhance magnetic ordering. Our results reveal that the electronic behavior of the ribbons is highly sensitive to both the stacking configuration and ribbon width, exhibiting metallic, semiconducting, and half-metallic characteristics. We find that multiple spin-polarized states emerge in the AB-α and AB-β stackings, where different interlayer and intralayer magnetic alignments lead to distinct electronic behaviors. In particular, we identify stacking-dependent half-metallic states, highlighting a mechanism for intrinsic spin filtering in these systems. Additionally, we show that an external electric field can effectively modulate the band structure of the ribbons, inducing a semiconductor-to-metal or half-metallic transition, depending on the field direction and intensity. These findings provide key insights into the tunability of spin-dependent electronic properties in α-graphyne bilayer systems, with potential implications for spintronic and nanoelectronic device applications.