Quantum friction between graphene sheets
  We study the Casimir friction phenomenon in a system consisting of two flat, infinite, and parallel graphene sheets, which are coupled to the vacuum electromagnetic (EM) field. Those couplings are implemented, in the description we use, by means of specific terms in the effective action for the EM field. They incorporate the distinctive properties of graphene, as well as the relative sliding motion of the sheets. Based on this description, we evaluate two observables due to the same physical effect: the probability of vacuum decay and the frictional force. The system exhibits a threshold for frictional effects, namely, they only exist if the speed of the sliding motion is larger than the Fermi velocity of the charge carriers in graphene. 
M. Bel\'en Farias, C\'esar D. Fosco, Fernando C. Lombardo and   Francisco D. Mazzitelli
hep-th cond-mat.mes-hall quant-ph