Dirac Plasmas in Graphene

Collective excitation of Dirac Fermions in graphene has many similarities to that of conventional semiconductor two dimensional electron gas (2DEG). For instance, the resonance frequency is proportional to q1/2, where q is the wave-vector. However, there are some fundamental differences. In this paper, we'll present our far-infrared spectroscopy studies of Dirac plasma in graphene. Localized plasmons in graphene disks and micro-ribbons are excited by far-infrared photons. The resonance frequency scales as n1/4 , where n is the sheet carrier density. This is distinctively different from conventional semiconductor. In addition, plasmons in graphene superlattice are compared to their counterparts in semiconductor superlattice.