This is an interesting
article on graphene research at Ga Tech.
Graphene apparently owes this enhanced mobility to the curious fact that its electrons and other carriers of electric charges behave as though they do not have mass. In conventional materials, the speed of electrons is related to their energy, but not in graphene. Although they do not approach the speed of light, the research team found that unbound electrons in graphene behave much like photons, massless particles that also move at a speed independent of their energy.