Loss induced amplification of graphene plasmons.

This Letter introduces a new mechanism to reverse and control the effect of losses in the plasmonic systems by using a coupled parity-time symmetric graphene waveguide with complex potentials. In order to explore the uncharted properties of parity-time symmetric graphene plasmons, this Letter analytically shows the plasmonic parity-time symmetry breaking in the coupled graphene waveguide by Sommerfeld integration. This phase transition leads to the distinct spatial propagation behaviors of graphene plasmons in the exact or broken parity-time symmetric phase driven by a point source. Particularly, a loss induced plasmonic amplification, as a characteristic of exceptional point behavior, is for the first time, to the best of our knowledge, revealed in the realm of graphene plasmonics.