Nonlinear broadening of the plasmon linewidth in a graphene stripe
  In contrast to semiconductor structures, the experimentally observed plasma resonances in graphene show an asymmetrical and rather broad linewidth. We show that this can be explained by the linear electron energy dispersion in this material and is related to the violation of the generalized Kohn theorem in graphene. 
S. A. Mikhailov and D. Beba
cond-mat.mes-hall