Illustration (IMAGE) Lobachevsky University Caption Fig. 1. (a) Illustration of a surface plasmon propagating along a graphene sheet at ?<0t<0. (b) Time dependence of the graphene carrier density. (c) Dispersion diagram showing the frequency transformation of the initial plasmon when the carrier density decreases from ?1N1 to ?2N2. Credit Lobachevsky University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.