Electrically Induced Dirac Fermions in Graphene Nanoribbons

Graphene nanoribbons are rapidly emerging as building blocks for carbon-based devices in the ultimate limit of scalability. Here, we investigate the response of armchair graphene nanoribbons to transverse electric fields on the basis of tight-binding Hamiltonians and ab initio calculations. Such fields can be achieved either upon electrical gating or by incorporating extrinsic impurities of opposite polarities along the nanoribbon. We demonstrate that the resulting field enforces a semiconductor-to-semimetal transition, with the semimetallic phase possessing zero-energy Dirac fermions that propagate along the armchair edges. This field-induced transition is inherent to group-IV honeycomb lattices, including silicene and germanene nanoribbons, irrespective of the type of edge termination. Overall, our findings open new avenues to electrically engineer Dirac semimetallic phases in otherwise semiconducting graphene-like nanoribbons.