▎ 摘　　要

Dirac cones discovered in classical periodic systems such as photonic and phononic crystals have exhibited many interesting properties, particularly conical dispersion at the Brillouin zone center can be related to a zero-refractive-index. Here, we theoretically and numerically explore the conical dispersion in plasmonic crystal of graphene nanodisks arranged in triangular lattice. We show that the plasmonic crystal of Dirac-like cone resulted from three-fold accidental degeneracy can be mapped to a zero-refractive-index medium around the Dirac-like point frequency of 65.5 THz. The isotropic behavior of Dirac-like point formed by a monopole and two dipoles is observed by calculating isofrequency contours. Furthermore, numerical simulations including cloaking, focusing and unidirectional transmission are implemented to demonstrate the zero-index characteristics of the graphene plasmonic crystal. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement