Shear viscosity of interacting graphene

The authors investigate here the hydrodynamic regime of ultraclean graphene, which has shown experimental signatures of flow phenomena. They propose that plasmons, a collective mode associated with charge density oscillations, form a collective fluid together with electrons and holes and demonstrate that plasmons significantly enhance the shear viscosity. Technically, the authors use a combination of a full numerical solution of coupled Boltzmann equations in combination with more phenomenological methods. This work sheds light on the potentially substantial role of collective modes in the hydrodynamic behavior of not only graphene but also two-dimensional electronic systems in general.