An Effective Approach to Achieve a Spin Gapless Semiconductor–Half‐Metal–Metal Transition in Zigzag Graphene Nanoribbons: Attaching A Floating Induced Dipole Field via π–π Interactions

Abstract

Under fi rst-principles computations, a simple strategy is identifi ed to modulate the electronic and magnetic properties of zigzag graphene nanoribbons (zGNRs). This strategy takes advantage of the effect of the fl oating dipole fi eld attached to zGNRs via π -π interactions. This dipole fi eld is induced by the acceptor/donor functional groups, which decorate the ladder-structure polydiacetylene derivatives with an excellent delocalized π -conjugated backbone. By tuning the acceptor/donor groups, -C≡C-number, and zGNR width, greatly enriched electronic and magnetic properties, e.g., spin gapless semiconducting, half-metallic, and metallic behaviors, with the antiferromagnetic − ferromagnetic conversion can be achieved in zGNRs with perfect, 57-reconstructed, and partially hydrogenated edge patterns. can produce potential differences between the edges of zGNRs and drive zGNRs into half-metal, even provide other appealing electronic features, e.g., spin gapless semiconductor, by changing the -C≡C-number of the PDA bridges. Note that PDA and its -C≡C-bridged ladder-structure derivatives have been synthesized experimentally, [71][72][73][74][75] and a PDA layer adhered on the graphene surface has been fabricated recently as a bimorph actuator with compelling advantages to the traditional electromechanical actuation technology, [ 76 ] and the electronic couplings of PDA nanowires on graphite have also been experimentally studied. [77][78][79] Moreover, the NO 2 /NH 2 decorated ladder-structure PDA derivatives linked with one -C≡C-bond were predicted to exhibit signifi cantly enhanced nonlinear optical (NLO) responses due to the excellent π -conjugated delocalization of the PDA backbone. [ 80 ] Here, we perform comprehensive density functional theory (DFT) computations to investigate the electronic and magnetic properties of the joint systems of zGNR and the decorated PDA derivatives, emphasizing the effects of different pairs of acceptor/donor groups, number of -C≡C-bonds in the PDA derivatives and the zGNR width, even the existence of edge 57-reconstruction in zGNRs. Our studies revealed that depositing the decorated PDA derivatives on perfect H-terminated zGNRs renders the joint systems the transition of SGS-halfmetal-metal, accompanied by the magnetic conversion from AFM to FM. Even with the existence of 57-reconstruction at the zGNR edges, abundant electronic and magnetic transitions of AFM SGS-FM half-metal-AFM metal-NM metal can also be observed in the joint systems. Moreover, through partially hydrogenating zGNRs at the 57-reconstructed edges, the effect of the edge reconstruction can be eliminated, and more fascinatingly, the electronic and magnetic properties of the joint systems based on edge-reconstructed wide zGNRs can be generally recovered to those of the corresponding joint systems with perfect narrow H-terminated zGNRs representing the remaining pristine zGNRs inside. DOIThese provide immensely valuable insights for facilitating the spintronic applications and effectively modulating the electronic an...

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