Plasmon electron-hole resonance in epitaxial graphene

The quasiparticle dynamics of the sheet plasmons in epitaxially grown graphene layers on SiC(0001) have been studied systematically as a function of temperature, intrinsic defects, influence of multilayers and carrier density. The opening of the inter-band loss channel appears as a characteristic upward shift in the plasmon dispersion and a dip in the width of the loss peak, which is explained as a resonance effect in the formation of electron-hole pairs. Despite the existence of strong electronic correlations, the plasmon dispersion can be quantitatively described within the framework of a nearly free electron gas.