The team has shown that graphene’s viscous fluid supports unidirectional electromagnetic waves on the edge. These “edge waves” are linked to a new topological phase of matter and symbolize a phase transition in the material, not unlike the transition from solid to liquid. A remarkable feature of this new phase of graphene is that light travels in one direction along the edge of the material and is robust to disorder, imperfections and deformation. Purdue researchers have harnessed this nonreciprocal effect to develop “topological circulators” – one-way routers of signals, the smallest in the world – that could be a breakthrough for on-chip, all-optical processing.

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