Fizeau drag in graphene plasmonics

Dragging of light by moving media was predicted by Fresnel(1) and verified by Fizeau's celebrated experiments(2) with flowing water. This momentous discovery is among the experimental cornerstones of Einstein's special relativity theory and is well understood(3,4) in the context of relativistic kinematics. By contrast, experiments on dragging photons by an electron flow in solids are riddled with inconsistencies and have so far eluded agreement with the theory(5-7). Here we report on the electron flow dragging surface plasmon polaritons(8,9) (SPPs): hybrid quasiparticles of infrared photons and electrons in graphene. The drag is visualized directly through infrared nano-imaging of propagating plasmonic waves in the presence of a high-density current. The polaritons in graphene shorten their wavelength when propagating against the drifting carriers. Unlike the Fizeau effect for light, the SPP drag by electrical currents defies explanation by simple kinematics and is linked to the nonlinear electrodynamics of Dirac electrons in graphene. The observed plasmonic Fizeau drag enables breaking of time-reversal symmetry and reciprocity(10) at infrared frequencies without resorting to magnetic fields(11,12) or chiral optical pumping(13,14). The Fizeau drag also provides a tool with which to study interactions and nonequilibrium effects in electron liquids.

Automated summary

The phenomenon of dragging light by moving media, predicted by Fresnel and verified by Fizeau, plays a key role in Einstein's special relativity theory. While experiments on dragging photons by an electron flow in solids have inconsistencies, the dragging of surface plasmon polaritons by an electron flow in graphene is a unique and complex phenomenon that challenges simple kinematics explanations.