Nano-infrared imaging of localized plasmons in graphene nano-resonators

We conduct in-situ near-field imaging of propagating and localized plasmons (cavity and dipole modes) in graphene nano-resonator. Compared with propagating graphene plasmons, the localized modes show twofold near-field amplitude and high volume confining ability (~10⁶). The cavity resonance and dipole mode of graphene plasmons can be effectively controlled through optical method. Furthermore, our numerical simulation shows quantitative agreement with experimental measurements. The results provide insights into the nature of localized graphene plasmons and demonstrate a new way to study the localization of polaritons in Van der Waals materials.