Field Enhancement and Gradient Force in the Graphene-Coated Nanowire Pairs

We investigate the field enhancement and gradient force in the graphene-coated nanowire pairs in this paper. The real part of modal index, normalized propagation lengths, surface charge distributions and field distributions of the six lowest orders' plasmon modes in the graphene-coated nanowire pairs is presented. Studies have shown that the six lowest orders' modes can be divided into two groups due to the monopole-monopole hybridizations or the dipole-dipole interactions. The field enhancement in the slot region of the graphene-coated nanowire pairs can be as large as 10(7) times, which is six orders' magnitude larger than the counterpart in silver nanowire pairs. Meanwhile, gradient force between the two nanowires can be as high as 20 nN center dot mu m(-1)center dot mW(-1), which is more than one order of magnitude (similar to 50 times) larger than the silver nanowire pairs and the previous results from other slot waveguides or coupled waveguides. The field enhancement or gradient force in the graphene-coated nanowire pairs may have applications in single biomolecule manipulation or detection.