Electrically Induced Dirac Fermions in Graphene Nanoribbons

TL;DR

This study demonstrates that applying transverse electric fields to graphene nanoribbons can induce a transition to a semimetallic phase with Dirac fermions, enabling electrical control of their electronic properties for device applications.

Contribution

The paper reveals that transverse electric fields can induce Dirac fermions in armchair graphene nanoribbons, a novel way to electrically engineer their electronic structure.

Findings

Electric fields induce a semiconductor-to-semimetal transition.

Dirac fermions propagate along nanoribbon edges in the semimetallic phase.

Transition critical fields scale inversely with nanoribbon width.

Abstract

Graphene nanoribbons are widely regarded as promising building blocks for next-generation carbon-based devices. A critical issue to their prospective applications is whether and to what degree their electronic structure can be externally controlled. Here, we combine simple model Hamiltonians with extensive first-principles calculations to investigate the response of armchair graphene nanoribbons to transverse electric fields. Such fields can be achieved either upon laterally gating the nanoribbon or incorporating ambipolar chemical co-dopants along the edges. We reveal that the field induces a semiconductor-to-semimetal transition, with the semimetallic phase featuring zero-energy Dirac fermions that propagate along the armchair edges. The transition occurs at critical fields that scale inversely with the width of the nanoribbons. These findings are universal to group-IV honeycomb lattices, including silicene and germanene nanoribbons, irrespective of the type of edge termination. Overall, our results create new opportunities to electrically engineer Dirac fermions in otherwise semiconducting graphene-like nanoribbons.